Preheat the oven to 375°F (190°C) and line a large baking sheet with parchment paper to prevent sticking and ensure a crisp base.
Lay the dough out on a flat, lightly floured surface and roll into a rectangle.
Spread a thin, even layer of Dijon mustard across the dough, leaving a 1/2-inch border at the edges.
Layer the turkey ham slices over the mustard, followed by an even layer of cheese slices.
Roll the dough tightly starting from the long edge to create a uniform log.
Wrap the log in plastic wrap and chill in the refrigerator for at least 30 minutes; this is crucial for achieving clean slices.
Using a sharp serrated knife, cut the chilled log into 1-inch thick rounds.
Place the pinwheels seam-side down on the prepared baking sheet.
In a small bowl, combine melted butter, poppy seeds, and garlic powder. Brush this mixture generously over each pinwheel.
Bake for 12-15 minutes, or until the pastry is golden brown and the cheese is bubbly.
Let cool slightly on a wire rack to maintain texture and garnish with fresh parsley before serving.