Preparation

• Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
• Roll out the puff pastry sheet on a lightly floured surface into a 10×12-inch rectangle. Spread Dijon mustard evenly over the surface.
• Sprinkle shredded Gruyère cheese over the mustard, leaving a ½-inch border around edges. Arrange apple slices in a single layer over cheese, then sprinkle with thyme and black pepper.
• Starting from one long side, tightly roll the pastry into a log. Slice into ½-inch thick rounds and place them cut-side up on the prepared baking sheet.
• Brush each pinwheel with beaten egg and sprinkle with flaky sea salt. Bake for 18-22 minutes, until puffed and golden brown.
• Let cool slightly before serving.