Custard-Filled Long John Doughnuts (Recipe)
Make 10–12 tender, custard-filled Long John doughnuts with enriched yeast dough, chilled pastry cream, and steady stovetop frying. Cook the custard to 82–85°C, cool it promptly, then fry small batches at 175–180°C. Fill only cooled doughnuts, keep them refrigerated, and use a deep, heavy pot with a thermometer for reliable results.
A filled doughnut can be frustrating when the outside browns before the center cooks, or when the custard leaks, tastes thin, or has not been cooled safely. The good news is that each problem has a practical fix: watch temperature, allow the dough to proof, and fill only after the doughnuts cool.
I make these in stages so the work feels manageable: cook the pastry cream first, prepare and proof the dough, then fry and fill. You will need a mixer or strong hands, a thermometer, a piping bag, and a deep, heavy pot. No oven is needed.
Recipe overview and equipment
This recipe makes 10–12 rectangular doughnuts with a soft, enriched crumb and vanilla pastry cream. “Enriched dough” means dough made with ingredients such as egg, sugar, and butter, which give it a tender texture. Allow time for chilling, proofing, and safe handling; the hands-on work is spread across several steps.
Use a heavy stainless-steel or enameled pot that sits securely on your burner. Heavy metal helps limit sharp oil-temperature drops when dough goes in. On induction, choose magnetic stainless steel or cast iron. Use a clip-on thermometer with its probe in the oil, clear of the pot bottom.
| Item | Amount or target | Why it matters |
|---|---|---|
| Milk for dough | 240 g, about 38°C (100°F) | Lukewarm, not hot |
| Bread flour | 500 g | Forms the dough structure |
| Frying oil | 5–7 cm (2–3 in) deep | Leave ample space above it |
| Frying temperature | 175–180°C (347–356°F) | Fry within this range |
| Pastry cream | About 35–45 g per doughnut | Fill through a side opening |
Do not use a coated vessel for deep frying unless its maker confirms it is suitable and gives clear temperature limits. Avoid unverified nonstick cookware. Set the pot on a stable burner, and keep the handle turned away from the edge. The thermometer, rather than a set preheating time, tells you when the oil is ready.
Ingredients and stovetop method
The method depends on two temperature checks: pastry cream reaches 82–85°C (180–185°F) to thicken, and oil stays at 175–180°C (347–356°F) for frying. “Pastry cream” is a cooked, egg-thickened custard. Stir it continuously as it cooks, then cool it promptly before filling the doughnuts.
Make and chill the pastry cream
Whisk 4 egg yolks, 100 g sugar, 30 g cornstarch, and a pinch of salt in a bowl. Heat 500 g whole milk in a saucepan until steaming, but do not let it boil. Slowly whisk the hot milk into the yolk mixture. This gradual mixing helps bring the eggs up in temperature without cooking them in lumps.
Pour the mixture back into the saucepan. Cook over medium heat, whisking continuously, until it reaches 82–85°C and is visibly thick. Remove it from the heat and whisk in 30 g butter and 5 g vanilla. Transfer the cream to a shallow container and cover its surface.
Cool from 57°C (135°F) to 21°C (70°F) within 2 hours, then from 21°C to 5°C (41°F) or below within 4 additional hours. A shallow container or ice bath can speed cooling; refrigerate the cream at 5°C or below. Keep it cold until you are ready to fill. Do not rely on thickness or appearance alone to judge cooking or cooling temperature.
Mix, proof, and shape the dough
Combine 240 g lukewarm milk, 7 g instant yeast, and 50 g sugar. Mix in 1 egg, 1 egg yolk, 500 g bread flour, and 8 g fine salt until a dough forms. Knead in 60 g softened unsalted butter a little at a time. Continue kneading until smooth and elastic, about 8–12 minutes in a mixer; kneading by hand may take longer.
Fry in controlled batches
Add oil to the pot to a depth of 5–7 cm, leaving ample headroom. Heat gradually to 175–180°C. Refined peanut oil has a typical smoke point near 227°C (440°F), but the smoke point varies by product. Use peanut oil only if allergies are not a concern. If oil smokes or smells degraded, turn off the heat and do not use it.
Fry 2–3 doughnuts at a time, depending on pot size. Lower them in carefully and turn once. They usually need about 1½–2 minutes per side, but size and oil recovery affect the timing. Keep the thermometer in the oil and adjust the burner to hold the target range. Between batches, wait for the oil to return to 175–180°C.
Lift the doughnuts onto a wire rack or absorbent paper. Let them cool until safe to handle before filling. Hot doughnuts release steam that can thin the custard and soften the crust. Never add cold water to hot cookware or hot frying oil; sudden contact can cause violent splattering and may damage some cookware.
Fill and finish
Fit a piping bag with a narrow filling tip and load it with cold pastry cream. Insert the tip into the side of each cooled doughnut and pipe about 35–45 g into it. One or more openings may be needed, depending on the tip and doughnut size. Stop when the doughnut feels filled but does not split or leak.
Dust with powdered sugar, or glaze with powdered sugar mixed with a small amount of milk. Apply the finish only after the doughnuts have cooled. Refrigerate filled doughnuts promptly at 5°C or below and serve the same day for best texture. Keep them chilled until serving, rather than leaving them at room temperature for an extended period.
Troubleshooting and practical batch checks
Most problems come from a missed temperature check, a rushed proof, or too many doughnuts in the pot. “Oil recovery” is the time the oil takes to return to its target temperature after dough is added. Check the thermometer between batches instead of assuming the oil is ready.
| What you notice | Likely cause | What to do |
|---|---|---|
| Doughnuts feel greasy | Oil temperature fell too low | Fry fewer at once; wait for 175–180°C |
| Outside browns too fast | Oil is too hot | Lower the burner and check the thermometer |
| Doughnuts are dense | Dough may be under-proofed | Let shaped pieces become puffy before frying |
| Custard is thin | It may not have reached cooking temperature | Cook while whisking to 82–85°C |
| Filling leaks out | Doughnut may be too hot or overfilled | Cool completely and pipe in measured amounts |
A useful kitchen scenario: if the first batch cools the oil below 175°C, do not add more dough just to keep moving. Pause and let the oil recover. If the custard has not met its cooling limits, do not use it as filling; continue cooling it safely instead. These checks take longer than guessing, but they prevent avoidable problems.
Serving, allergens, and cleanup
Filled doughnuts have the best contrast when the dough is tender, the custard is cold, and the finish is light. For a neat cross-section, cut one just before plating with a sharp serrated knife. Tell guests that the recipe contains wheat, egg, and milk, and disclose peanut oil if you use it.
Turn off the burner and let the oil cool completely before handling it. Strain and store oil only if it remains clean, unburnt, and suitable for reuse. Otherwise, dispose of it according to local guidance; never pour oil down a drain. Wash stainless steel with warm water, detergent, and a non-scratch sponge, then dry it promptly. For cast iron, follow the maker’s care instructions and dry it well.
Wash pastry-cream tools and work surfaces promptly with hot detergent solution. Keep tools used with raw eggs separate from ready-to-eat custard and finished doughnuts, and sanitize food-contact surfaces as required by your food-safety plan. The key next step is simple: chill the cream, control the oil, and fill only cooled doughnuts.
Frequently asked questions
These answers cover the common timing, temperature, and storage questions for homemade custard-filled Long Johns. Use the thermometer targets as your guide, since dough size, room temperature, and burner strength can change cooking times.
Can I make the pastry cream ahead?
Yes. Cook it, transfer it to a shallow container, cover its surface, and cool it within the stated time limits. Refrigerate at 5°C (41°F) or below and keep it chilled until filling. Do not leave it out while the dough rises.
What temperature should the oil be?
Keep the frying oil at 175–180°C (347–356°F). Check it with a thermometer, including between batches. If adding dough drops the temperature below the range, wait for it to recover before frying more.
How many doughnuts should I fry at once?
Fry 2–3 at a time, depending on the size of your pot. Smaller batches make it easier to maintain oil temperature. Leave enough room for the doughnuts to move without crowding the pot.
How do I know when the custard is cooked?
Whisk continuously over medium heat until the pastry cream reaches 82–85°C (180–185°F) and visibly thickens. Use a thermometer rather than appearance alone. Remove it from the heat and whisk in the butter and vanilla.
Can I fill the doughnuts while they are warm?
Wait until they have cooled and are safe to handle. Filling hot doughnuts can trap steam, which may thin the custard and soften the crust. Cold pastry cream also holds its texture better during filling.
How much custard goes in each doughnut?
Start with about 35–45 g of pastry cream per doughnut. Pipe it through a side opening and stop before the doughnut splits or filling leaks out. The exact amount depends on the size and shape of each piece.
Can I use peanut oil?
Refined peanut oil is an option if peanut allergy is not a concern. Its typical smoke point is near 227°C (440°F), but products vary. Do not use oil that smokes or smells degraded, and disclose peanut oil to guests.
How should I store filled doughnuts?
Refrigerate them promptly at 5°C (41°F) or below and serve the same day for best texture. Keep them chilled until serving. Do not hold pastry-cream-filled doughnuts at room temperature for an extended period.
Why did my doughnuts turn greasy?
The oil may have dropped below the frying range, often because too many doughnuts went in at once. Fry smaller batches and wait for the oil to return to 175–180°C before starting the next batch.
Can I pour hot oil down the sink?
No. Let the oil cool completely, then strain and reuse it only if it remains clean and suitable. If it is spent, follow local disposal guidance. Never pour oil down a drain.
(This article was written by one of our staff writers, Steven R. Bancroft. Visit our Meet the Team page.)
