Berliner

1. A few hours before, start by preparing the pastry cream.

Pastry cream

1. Mix the cornstarch and the flour and sift them.
2. Heat the milk and the split vanilla bean. Bring to a boil turn off the heat.
3. In a bowl of a stand mixer, beat the yolks and sugar until the mixture is white.
4. Add the flour and cornstarch mixture gradually using a whisk. The mixture obtained should be homogeneous and smooth.
5. Whisk the mixture with half of the milk, without lathering.
6. The mixture should be smooth and without too many bubbles.
7. Pour the resulting mixture into the saucepan containing the rest of the milk and bring to a low heat, whisking constantly. When the cream is thickened, stop cooking.
8. Dab the surface of the cream with a knob of butter to prevent the formation of a "skin" while cooling.
9. Cover with plastic wrap (by having the plastic wrap touch the cream) and reserve in the refrigerator for 3 to 4 hours.

Donut dough

1. Cut out about 20 4-inch (10 cm) squares of parchment paper.
2. In the bowl of a food processor, mix the flour and active dry yeast.
3. Add the warm milk gradually and knead for 1 minute.
4. Stir in the lemon zest, sugar, salt and egg.
5. Knead for 15 minutes at medium speed until the dough detaches from the sides of the bowl.
6. Then add half of the butter at a time, while kneading for 5 minutes, at medium speed, until it is well incorporated.
7. Cover with a cloth and let it rise for 2 hours, away from drafts.
8. Flour the work surface.
9. Take the dough out of the bowl and divide it into about 20 pieces of about 2 oz (60 g) each.
10. Form balls and flatten them slightly with a rolling pin (the dough should be smooth).
11. Drop them as you go on the squares of parchment paper (1 piece of dough per square).
12. Cover them with a cloth and let them rise again for 30 minutes, away from drafts.
13. In a large pan, heat a large amount of vegetable oil to a temperature of about 330 F / 170 C, and plunge the donuts, 3 at a time. The temperature of the oil should not rise above 340 F / 170 C.
14. Use the parchment paper to slide them in the hot oil, this technique helps to keep their shape.
15. Fry about 40 seconds on each side.
16. Drain the donuts in a colander. Let cool.

Assembly of the Berliner

1. Remove the pastry cream from the refrigerator and beat vigorously. If it is too stiff, add 1 or 2 tablespoons of warm milk.
2. Pour the pastry cream in a piping bag with a fluted socket.
3. Cut the donuts in half and garnish with the pastry cream.
4. Sprinkle icing sugar before serving.