01 -
In the bowl of a stand mixer, add both flours, sugar, and yeast. Stir briefly to blend.
02 -
Scatter the softened butter pieces over the flour mixture. Add the eggs, lukewarm milk, vanilla, and salt.
03 -
Using a dough hook, knead at low speed for 10 minutes until smooth, elastic, and slightly tacky.
04 -
Grease a clean bowl with oil, place the dough in the bowl, cover with plastic wrap, and let rise for 2–3 hours until tripled in size.
05 -
Punch down risen dough, roll to 1.5 cm thickness, and cut circles with a round cutter. Let rise again for 1–1.5 hours until tripled.
06 -
In a large, deep pot or pan, heat frying oil to 170°C (337°F).
07 -
Fry doughnuts in batches for 2 minutes on each side until golden brown. Drain on kitchen paper and roll in sugar.
08 -
Make an incision in cooled doughnuts and pipe pastry cream or another filling into each.
09 -
Whisk egg yolks, sugar, vanilla, and lemon zest. Add cornstarch, then temper with warm milk. Cook until thickened, cool completely.