Vanilla Custard Doughnuts

Instructions

Doughnut dough

1. Add the warm milk and stir in the yeast and sugar to the bowl of a stand mixer fitted with a dough hook. If using active dry yeast, let this sit for 5-10 minutes until foamy.
2. Add the egg, flour, and salt to the milk mixture. Turn the mixer on low speed or use your hands to combine until it forms a sticky, thick dough. Mix this dough for around 2 minutes to begin developing the gluten. 
3. Add the room-temperature butter. Turn the mixer on medium speed until the sticky dough strengthens and comes together. In the mixer, it should pull away cleanly from the sides of the bowl. Mix the dough for at least 10 minutes for the best gluten development. The dough should feel smooth, soft, and strong.
4. Shape the dough into a ball and place it into a lightly greased large bowl. Cover the bowl with plastic wrap and let it proof in a warm spot until doubled in size. You can also proof the dough in the refrigerator overnight for extra flavor.

Custard

1. In a medium saucepan, heat the milk until it is just at a simmer - don't let it boil.
2. While the milk is warming, add the egg yolks, sugar, salt, vanilla, and cornstarch in a separate bowl until smooth
3. Place the bowl on a dampened kitchen towel to prevent slipping. Add the hot milk mixture to the egg mixture in a steady stream while whisking.
4. Return the combined mixture to the saucepan over medium heat, whisking constantly until it bubbles. Once it starts bubbling, it will begin to thicken. Keep it at a bubble don't stop whisking for 1 minute.
5. Take it off the heat and whisk in the butter until thoroughly combined. Pour the hot pastry cream into a clean bowl. If you want an extra silky smooth texture, you can push it through a fine mesh sieve first
6. Lay a piece of plastic wrap directly onto the surface of the custard to avoid a skin forming. Let it come to room temperature, then chill it in the refrigerator until completely cold.

Shaping and frying

1. Punch down the dough and pull it from the bowl onto a lightly floured surface. If it is refrigerated, it will be stiff. Form it into a mound and lightly flour the top. Then roll it into a ½ inch/ 1.3cm thick rectangle.
2. Use a cookie cutter or jar lid to cut out round donuts about 3.5 inches/9 cm in diameter. Place each cut donut onto some parchment paper.
3. Any dough scraps can be kneaded back into a ball and rolled out again. Leave the dough scraps to rest for a few minutes before rolling out again. This allows the gluten to rest again so the dough doesn't spring back when rolled.
4. Let the donuts rest for 30-60 minutes until they are puffy. If drying out, lightly brush the tops with a bit of water. Use kitchen scissors to cut around each donut on the parchment paper so each donut sits on its piece.
5. When nearly ready to fry, pour the frying oil into a deep fryer or a deep pot and heat it to around 340°F / 171°C - 347°F / 175°C. Fill a shallow bowl with caster sugar.
6. Carefully drop 1-2 donuts into the oil and remove the parchment paper with tongs. Fry the donuts for 2 minutes on one side, flip them, and fry for 2 minutes on the other.
7. Ensure the oil in the pot stays hot, but don't let it surpass 350°F / 177°C, or the donuts will burn before they can cook in the middle.
8. Remove the fried donuts with a slotted spoon, let them cool on a wire rack, and continue frying the rest.  Once cooled, toss the doughnuts in a seperate bowl of granulated or caster sugar to coat.

Filling

1. Give the cold custard a whisk to loosen it up, then spoon it into a piping bag with a round tip. Insert the tip of a small knife into the sides of the cooled doughnuts to make a hole for the filling. Pipe the custard through the hole into each donut.

Once filled, custard doughnuts are best served on the day they are made. Store any leftover custard doughnuts in an airtight container in the refrigerator.