Prepare the spinach filling: Finely chop the thoroughly dried fresh spinach. In a medium bowl, combine the softened cream cheese, grated Parmesan cheese, chopped spinach, garlic powder, salt, and black pepper. Mix well until all ingredients are evenly incorporated and you have a smooth, spreadable mixture.

Prepare the puff pastry: Lightly flour a clean work surface. Unfold one sheet of thawed puff pastry. If the pastry is still cold and stiff, let it sit at room temperature for 5-10 minutes until pliable but not sticky. Roll it out slightly to ensure an even thickness, aiming for a rectangle approximately 25cm x 30cm (10 x 12 inches).

Spread the spinach mixture: Evenly spread half of the spinach and cheese mixture over the entire surface of the puff pastry sheet, leaving a small border of about 1cm (0.4 inches) along one of the longer edges. This border will help seal the roll.

Roll up the pastry: Starting from the long edge opposite the clean border, carefully and tightly roll up the puff pastry sheet into a log. Press gently to ensure the log is compact. Use the clean border to seal the edge by lightly pressing it down.

Chill the spinach log: Wrap the rolled pastry log tightly in plastic wrap. Place it in the refrigerator for at least 30 minutes (or up to 2 days) to firm up. This makes it much easier to slice cleanly.

Repeat for the pesto filling: Lightly flour your work surface again and unfold the second sheet of puff pastry. Roll it out to the same approximate dimensions as the first (25cm x 30cm / 10 x 12 inches). Spread the basil pesto evenly over the surface, leaving a 1cm (0.4 inch) border on one long edge. If using, sprinkle the pine nuts over the pesto.

Roll up the pesto log: Similar to the first log, starting from the long edge opposite the clean border, tightly roll up the puff pastry. Press gently to seal the edge with the clean border.

Chill the pesto log: Wrap the pesto-filled pastry log tightly in plastic wrap and refrigerate for at least 30 minutes, alongside the spinach log.

Preheat the oven and prepare baking sheets: Preheat your oven to 200°C (400°F). Line two large baking sheets with parchment paper.

Prepare the egg wash: In a small bowl, whisk together the egg and 1 tablespoon (15ml) of water. This will give the pinwheels a beautiful golden sheen.

Slice the pastry logs: Remove the chilled pastry logs from the refrigerator. Unwrap them. Using a sharp knife, carefully slice each log into 1.5cm (about 0.6 inches) thick rounds. You should get approximately 15 pinwheels from each log.

Arrange and brush the pinwheels: Place the sliced pinwheels cut-side down onto the prepared baking sheets, leaving about 2.5cm (1 inch) of space between them to allow for expansion. Brush the tops and sides of each pinwheel generously with the egg wash.

Bake the pinwheels: Bake in the preheated oven for 15-20 minutes, or until the puff pastry is golden brown, puffed up, and cooked through. Rotate the baking sheets halfway through the baking time to ensure even browning.

Cool and serve: Once baked, remove the pinwheels from the oven and let them cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely. Serve warm or at room temperature.