Nutella-Stuffed Bomboloni

Let 6 tablespoons unsalted butter sit at room temperature until softened, about 1 hour.

Warm 1 cup whole milk in 15-second intervals in the microwave or in a small saucepan over low heat until warm, 100 to 110°F. Pour into a stand mixer. Sprinkle with 1 packet active dry yeast and 1 teaspoon of the granulated sugar and stir to combine. Let sit until foamy, about 5 minutes. (If not foamy, the yeast is dead and you should start over.)

Add 4 cups all-purpose flour, 1/4 cup of the granulated sugar, softened butter, 2 large eggs, 1 teaspoon kosher salt, and 1 teaspoon vanilla extract. Mix with the dough hook attachment on low speed until the flour is incorporated. Increase the speed to medium and mix until the dough has come together and is smoother but still sticky, 8 to 10 minutes.

Scrape the dough onto a lightly floured work surface. Knead with your hands a few times until it forms a ball. Lightly grease a large bowl with canola oil. Add the dough and flip to coat in the oil. Cover with a clean dish towel or plastic wrap and let rise in a warm place until doubled in size, about 1 hour.

Line 2 baking sheets with parchment paper. Transfer the dough to a lightly floured work surface. Roll out until 1/2-inch thick. Using a 3-inch round cutter, cut out as many rounds as possible and transfer to the baking sheets. Gather the dough scraps, roll out again, and and cut out more doughnuts. If the dough is springy and difficult to roll out, let it rest for several minutes before rolling again.

Cover the baking sheets loosely with clean dish towels or plastic wrap. Let rise in a warm place until puffed, about 1 hour. Meanwhile, line a third baking sheet with paper towels. Place the remaining 1 cup granulated sugar in a medium bowl.

Heat 2 quarts canola or vegetable in a large Dutch oven or heavy-bottomed pot over medium-high heat until 350°F.

Fry the doughnuts in batches of 3 to 4: Gently add the doughnuts to the hot oil and fry until deep golden-brown on the bottom, 2 to 3 minutes. Flip the doughnuts and fry until puffed and the second side is deeply golden-brown, 2 to 3 minutes more. Using a metal spider or slotted spoon, carefully transfer the doughnuts to the paper-towel lined baking sheet.

While the next batch is frying, add the just-fried doughnuts to the bowl of sugar one at a time and toss to coat. Return to the baking sheet. Let the doughnuts cool for 15 minutes before filling.

Scrape about 1 1/2 jars Nutella into a piping bag fitted with a large round piping tip. Insert the tip of a small knife or chopstick into the side of each doughnut and rotate to make a small hole for the filling. Pipe the Nutella through the hole into each doughnut, adding more Nutella to the piping bag as needed. Squeeze any unused Nutella back into the jar for future use. Serve the bombelone immediately.