Combine softened cream cheese, Parmesan cheese, mayonnaise, garlic powder, onion powder, and pepper in a mixing bowl. Blend until smooth and creamy. Fold in thawed spinach until evenly incorporated.

Lightly flour your work surface and unroll the puff pastry sheet. Flatten it slightly with a rolling pin. Spread the spinach filling evenly over the pastry, leaving a half-inch border.

Starting from the filled edge, tightly roll the pastry towards the border, pinching the edges to secure the filling.

Wrap the roll in plastic wrap and chill in the refrigerator for at least 30 minutes.

Preheat your oven to 400°F (200°C).

Slice the chilled roll into half-inch thick pieces and arrange on a lined baking sheet. Brush with egg wash.

Bake for 15-20 minutes until puff pastry is golden brown. Let cool slightly before serving.