Drain 10 oz thawed frozen spinach and wring out any extra moisture using a mesh cloth or kitchen towel.
Transfer to a medium mixing bowl, then mix in ½ cup shredded sharp cheddar cheese, ½ cup shredded, low-moisture mozzarella cheese, 2-3 Tablespoons grated parmesan, ¼ teaspoon garlic powder, ¼ teaspoon onion powder, and ¼ teaspoon salt until well combined.
Roll two sheets of thawed puff pastry dough out onto a lightly floured surface. Spread half the spinach mixture evenly onto each pastry, leaving a ½-inch border.
Starting from the long side, roll each pastry tightly into a log. Slice into 1–1¼ inch rounds using a sharp knife. Repeat with the second pastry sheet.
Place pinwheels on a parchment-lined baking sheet and refrigerate for 15–20 minutes.
Preheat your oven to 400°F.
Once the rolls have chilled, brush the tops lightly with an egg wash (1 large beaten egg mix with 1 Tablespoon water).
Bake 18–22 minutes, until puffed and deeply golden.
Let rest for 5 minutes so the cheese sets before serving.
