In a large bowl of a stand mixer fitted with a dough hook attachment, combine the warm water, sugar, and yeast and let sit for 5 minutes.
1 cup warm water, 3/4 teaspoon sugar, 1/2 Tablespoon active dry yeast
After the yeast has proofed for 5 minutes and is foamy, add the salt and 1 cup of flour and mix well. Continue to add the remaining flour, kneading until smooth for about 5 minutes.
1 teaspoon salt, 2 1/4 to 2 1/2 cups all-purpose flour
Use the olive oil to lightly grease a clean bowl and transfer the dough to the bowl, giving it a quick turn to coat in the oil. Cover with plastic wrap and let rest for 30 minutes.
2 Tablespoons olive oil
Preheat oven to 400°F for at least 20 minutes. While the oven preheats, roll the dough into a large, thin rectangle. Top with the ground beef, marinara sauce, and mozzarella cheese, leaving a 2-inch border around the sides.
3/4 pound ground beef, 1 1/2 cups mozzarella cheese, 1/2 cup marinara or pizza sauce
Brush the border with the egg wash, then fold the short ends over the edges of the filling and roll the stromboli into a cylinder-shaped log.
1 large egg
Transfer the stromboli to an overturned baking sheet lined with parchment paper with the seam side down. Brush the top with remaining egg wash (if desired) and cut diagonal gashes across the top with a sharp knife. Bake in the preheated oven for 25-30 minutes until browned on top and cooked through.
Let rest for 10 minutes before slicing. Serve with marinara sauce or ranch dressing on the side.