01 -
Mix flour, salt, and sugar in a large bowl. Create a well in the center and pour in the warm milk. Sprinkle yeast over milk and let it sit until foamy, about 5 minutes. Add the softened butter and beaten eggs, then knead until the dough becomes smooth and silky, about 8 minutes by hand or with a mixer on low speed.
02 -
Shape the dough into a ball and place in a lightly greased bowl. Cover with a damp kitchen towel and let rise in a warm spot until doubled in size, about 90 minutes.
03 -
While the dough rises, make the custard filling. Warm the milk in a saucepan. In a bowl, whisk together egg yolks, sugar, and cornstarch. Slowly pour half the warm milk into the egg mixture while whisking, then return everything to the saucepan. Cook over medium heat, stirring constantly, until thick. Remove from heat, stir in vanilla, and let cool completely.
04 -
Roll out the risen dough on a lightly floured surface to about 1/2 inch thickness. Use a 2¼-inch round cutter to cut circles. Place them on a parchment-lined baking sheet, cover with a light cloth, and let rest for 10 minutes.
05 -
Heat about an inch of vegetable oil in a deep pan to 350°F. Carefully drop 5-6 dough rounds into the hot oil at a time. Fry until golden brown on one side (about 2 minutes), then flip and cook the other side. Remove with a slotted spoon and drain on paper towels.
06 -
Once the bomboloni have cooled slightly, use a small knife to make a slit in the side of each one. Fill a piping bag with the cooled custard and pipe about a teaspoon into each pastry until pleasantly plump but not bursting.
07 -
Dust the filled bomboloni generously with powdered sugar just before serving. These are best enjoyed warm or at room temperature on the day they're made.