Prepare the Filling: In a mixing bowl, blend softened cream cheese, Parmesan, mayonnaise, garlic powder, onion powder, black pepper, and thoroughly drained spinach. Mix until it reaches a smooth and creamy consistency.

Roll Out Pastry: On a lightly floured surface, unroll the puff pastry sheet. Spread the spinach mixture evenly over the pastry, leaving a small margin at one edge to create a seal when rolled.

Form the Log: Starting from the edge with the filling, tightly roll the pastry towards the empty edge. Ensure it’s snug to maintain its shape while baking.

Chill: Wrap the rolled pastry log in plastic wrap and place it in the refrigerator for at least 30 minutes.

Preheat Oven: While the log chills, preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

Slice & Brush: Once chilled, remove the log from the fridge and slice it into half-inch rounds. Arrange them on the prepared baking sheet. Beat an egg with a splash of water, then brush it over the tops and sides of each pinwheel.

Bake: Place the baking sheet in the oven and bake for 15-20 minutes, until the pinwheels are puffed and golden brown. Let them cool slightly before serving.