How to make it

1. In a large bowl, combine flour, sugar, salt, and yeast.
2. Add warmed milk, melted butter, and egg to the dry ingredients. Mix until a dough forms.
3. Knead the dough on a floured surface for about 5 minutes until smooth.
4. Place the dough in a greased bowl, cover, and let rise in a warm place for 1 hour or until doubled in size.
5. For the custard filling, heat milk in a saucepan until just simmering.
6. In a bowl, whisk together sugar, cornstarch, salt, and egg yolks.
7. Gradually whisk the hot milk into the egg mixture, then return to the saucepan.
8. Cook over medium heat, whisking constantly, until thickened. Remove from heat and stir in vanilla.
9. Cover with plastic wrap directly on the surface and chill for 1 hour.
10. Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.
11. Roll out the dough to 1/2-inch (1.3 cm) thickness. Cut into rounds using a 3-inch (7.5 cm) cutter.
12. Place on the prepared baking sheet, cover, and let rise for 20 minutes.
13. Bake for 10-12 minutes until lightly golden. Cool on a wire rack.
14. For the glaze, heat cream in a saucepan until just simmering.
15. Pour over chopped chocolate and let sit for 2 minutes, then stir until smooth.
16. Stir in butter until glossy.
17. Once doughnuts are cool, fill each with custard using a piping bag.
18. Dip the tops of each doughnut into the chocolate glaze.