Step 1: Prepare the Ingredients

1. Preheat the oven to 375°F (190°C) and line a large baking sheet with parchment paper.
2. Cook the bacon until crispy, then crumble it into small pieces. Alternatively, cook and crumble breakfast sausage. Set aside.
3. Sauté the diced onion and bell pepper in a skillet over medium heat for 3–4 minutes, or until softened. Add the spinach (if using) and cook for 1 more minute. Remove from heat and set aside.

Step 2: Make the Scrambled Eggs

1. In a medium bowl, whisk the eggs, milk, salt, and black pepper until well combined.
2. Heat the butter in a nonstick skillet over medium-low heat. Pour in the egg mixture and cook, stirring gently with a spatula, until the eggs are soft and just set. Avoid overcooking, as the eggs will cook further in the oven. Remove from heat and set aside to cool slightly.

Step 3: Roll Out the Dough

1. On a lightly floured surface, roll out the pizza dough into a large rectangle, approximately 12×15 inches. The dough should be thin but not so thin that it tears.

Step 4: Assemble the Stromboli

1. Spread the scrambled eggs evenly down the center of the dough, leaving about 1 inch of space around the edges.
2. Top the eggs with the sautéed veggies, followed by the crumbled bacon or sausage.
3. Sprinkle the cheddar and mozzarella cheeses evenly over the filling.

Step 5: Fold and Seal the Stromboli

1. Carefully fold one long side of the dough over the filling, then fold the other side over to overlap slightly.
2. Pinch the seams together to seal, then tuck the ends underneath to create a tight seal. Transfer the Stromboli to the prepared baking sheet, seam-side down.

Step 6: Add the Egg Wash

1. Brush the top and sides of the Stromboli with the beaten egg to create a golden, glossy crust.
2. Sprinkle sesame seeds or everything bagel seasoning on top, if desired.

Step 7: Bake the Stromboli

1. Bake in the preheated oven for 20–25 minutes, or until the Stromboli is golden brown and the filling is hot and bubbly.
2. Let the Stromboli cool for 5 minutes before slicing into thick slices.

Step 8: Serve and Enjoy

1. Garnish with fresh parsley and serve with your favorite dipping sauces, such as hot sauce, ketchup, or salsa.