1. Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
2. Roll out the pizza dough on a lightly floured surface into a rectangle, about 12×16 inches.
3. Spread the Dijon mustard evenly over the dough, leaving a 1-inch border on all sides.
4. Layer the shredded chicken, slices of ham, and Swiss cheese over the mustard.
5. Carefully roll the dough from one long side to the other, like a jelly roll, tucking in the ends as you go.
6. Place the stromboli seam-side down on the prepared baking sheet. Brush the top with the beaten egg for a golden finish.
7. Mix the melted butter with garlic powder and parsley, then brush it over the stromboli.
8. Bake for 25-30 minutes, or until the crust is golden brown and crisp.
9. Allow to cool for a few minutes before slicing and serving.

Remember, the kitchen is a place of experimentation. Don’t be afraid to try different filling combinations or spices—your taste buds will thank you!