Making the Dough

Activate the Yeast: In the bowl of your stand mixer (or a large bowl), gently whisk together the warm milk, sugar, and yeast. Let it sit for 5-10 minutes until it becomes foamy.

Mix the Dough: To the foamy yeast mixture, add the flour, salt, and egg. Mix with the dough hook on low speed until a shaggy dough forms. Add the softened butter and continue to knead on medium speed for 6-8 minutes, until the dough is smooth, elastic, and pulls away from the sides of the bowl.

Let it Rise (First Proof): Form the dough into a ball and place it in a lightly oiled bowl, turning to coat. Cover with plastic wrap or a damp towel and let it rise in a warm, draft-free spot for 1-1.5 hours, or until doubled in size.

Assembling and Baking

Cook the Filling: While the dough is rising, brown the ground beef in a large skillet over medium-high heat until no longer pink. Drain off all the excess grease. Stir in the Worcestershire sauce, salt, and pepper. Let it cool completely, then stir in the shredded cheddar cheese.

Divide and Shape the Dough: Gently punch down the risen dough. On a lightly floured surface, divide it into 12 equal pieces. Roll each piece into a smooth ball.

Stuff and Seal the Bombs: Take one ball of dough and flatten it into a 4-inch circle. Spoon about 2-3 tablespoons of the cheesy beef mixture into the center. Gently pull the edges of the dough up and over the filling, pinching the seams together very tightly to seal. Place seam-side down on a parchment-lined baking sheet.

Let it Rise (Second Proof): Cover the assembled bombs loosely with plastic wrap and let them rest for another 20-30 minutes. They will puff up slightly. Meanwhile, preheat your oven to 375°F (190°C).

Brush and Bake: In a small bowl, mix the melted butter and garlic powder. Brush this mixture generously over the tops of the bombs. Sprinkle with parmesan cheese and sesame seeds. Bake for 18-22 minutes, or until deep golden brown.