In a small bowl, dissolve yeast in warm milk with 1 tablespoon sugar. Let sit for 5–10 minutes until foamy.

In a large bowl, mix flour, remaining sugar, and salt.

Add yeast mixture, eggs, and softened butter. Mix until a soft dough forms.

Knead dough on a lightly floured surface for 5–7 minutes until smooth and elastic.

Place dough in a greased bowl, cover, and let rise in a warm place for 1 hour or until doubled.

Punch down dough and roll out to 1/2-inch thickness. Cut out circles with a 3-inch cutter.

Place dough circles on a floured surface, cover, and let rise another 30 minutes.

Heat oil in a deep pan to 350°F. Fry doughnuts 2–3 minutes per side until golden brown.

Drain on paper towels, then roll warm bomboloni in sugar.

If filling, use a piping bag to inject jam, Nutella, or custard into the center.