1. Prepare the Dough:

In a large bowl or stand mixer, combine the flour, salt, and sugar. Create a well in the center.

Pour the warmed milk into the well, then sprinkle the yeast over it. Let it sit for 5 minutes to foam.

Add the softened butter and beaten eggs, then knead the dough until smooth and silky (about 8 minutes on low speed or by hand).

2. First Rise:

Form the dough into a ball and place it in a greased bowl. Cover with a damp cloth.

Let the dough rise in a warm place for about 90 minutes, or until doubled in size.

3. Shape the Bomboloni:

Roll the dough onto a lightly floured surface to about 1/2 inch thickness.

Use a 2¼-inch cookie cutter to cut out rounds.

Place the rounds on a parchment-lined baking sheet, cover with a cloth, and let them rest for 10 minutes (or 5 minutes in a warm kitchen).

4. Fry the Bomboloni:

Heat about 1 inch of vegetable oil in a deep pan over medium-low heat to 350°F (175°C).

Fry the bomboloni in small batches, turning them carefully with a slotted spoon until golden brown on both sides. Drain on paper towels and allow to cool slightly.

5. Fill the Bomboloni:

Use a small paring knife to make a slit in the center (or side) of each bombolone.

Fill a piping bag with custard and pipe about a teaspoon of filling into each pastry.

6. Finish and Serve:

Dust the filled bomboloni with powdered sugar.

Serve warm or at room temperature.