Preheat Oven: Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.
Prepare Dough: On a lightly floured surface, roll out the pizza dough into a large rectangle (about 12x14 inches).
Add Mustard (Optional): If using Dijon mustard, spread it evenly over the dough, leaving a 1-inch border around the edges.
Layer Ingredients: Evenly layer the ham slices on top of the dough, followed by the Swiss cheese.
Roll It Up: Starting from one of the longer sides, carefully roll the dough into a tight log, tucking the ends under as you roll. Place the seam side down on the prepared baking sheet.
Brush with Egg Wash: Brush the beaten egg over the top of the stromboli to give it a golden, glossy finish.
Season the Top: Drizzle the top with olive oil and sprinkle with garlic powder and Italian herbs if desired.
Bake: Bake for 20-25 minutes, or until the stromboli is golden brown and cooked through.
Cool and Slice: Allow the stromboli to cool for a few minutes before slicing. Serve warm with marinara sauce on the side for dipping.