Dissolve the yeast in a small bowl with a scant 1/4 cup cold water. Place the flour, sugar, salt and eggs in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed until the ingredients are dispersed, about 5 seconds. Add the dissolved yeast and beat for about 2 minutes on medium-high speed, until the dough is well combined and holds together. Add the cubed butter and mix for another 5 to 7 minutes, until the dough no longer sticks to the side of the mixing bowl. If the dough is overly sticky, you may need to add about 1 tablespoon of flour. It is usually necessary to scrape down the side of the bowl with a rubber spatula to encourage the dough to form a ball and come away from the side. Remove the paddle and pat the dough into a ball at the bottom of the bowl. Cover the mixing bowl with plastic wrap and let the dough rest at room temperature for about 20 minutes. The dough will rise slightly.
Remove the dough from the mixing bowl and punch it down to remove the air. Spread it onto a lightly floured baking sheet with your fingers and flatten the dough until it is about 3/4-inch thick. Cover with plastic wrap and let it rest in the refrigerator for a minimum of 2 hours or overnight. It will slightly proof.
Remove the dough from the refrigerator and place on a lightly floured work surface. Flatten it slightly with your hands. Cut the dough into circles with a 1 1/2-inch diameter cutter, keeping the cuts as close together as possible. Pat any leftover dough into a rectangle and cut more circles out of it. (At this stage, the bombolini can be frozen for up to 1 week if wrapped well in plastic wrap. Allow the bombolini to defrost in the refrigerator before proofing.)
Place the bomboloni on a parchment covered baking sheet lightly sprayed with nonstick spray. Space them 2 inches apart. Loosely cover the baking sheet with plastic wrap. Allow the bomboloni to proof at room temperature for about 2 hours, until they have doubled in size and appear light and full of air.
Heat enough oil about 15 minutes in an electric fryer or in a 4-quart heavy-bottomed saucepan over medium-high heat to 320 degrees F. If using a saucepan, check the temperature with a candy thermometer. Fry 5 to 7 bomboloni at one time, any more than that and the oil temperature will dip down too much and they will not fry evenly. Fry until they are golden brown, a total of 3 to 5 minutes. Turn as needed to evenly fry each side. As they fry, they will increase in size. Remove the bomboloni with a large slotted spoon and set on a paper towel to drain the excess oil.
While the bomboloni are still warm, roll them in a bowl filled with granulated sugar until evenly coated. If desired, fill the bomboloni with a raspberry jam-filled pastry bag fitted with a 1/4-inch plain tip. Use a sharp paring knife to make a small hole on the bottom of each bomboloni. Place the tip of the pastry bag in the hole and squeeze until the bomboloni feels heavy. It is best to fill the bomboloni while they are still warm and the dough is soft and pliable. Serve immediately.
Recipe courtesy of Bomboloni, 2011