Preheat your oven to 400°F (200°C). Roll out thawed puff pastry into a 10x14-inch rectangle and transfer it to a parchment-lined baking sheet. Score a 1-inch border and prick the center before baking for 12-15 minutes until golden brown.

In a mixing bowl, whisk together the eggs, Greek yogurt, minced garlic, and salt until smooth. Fold in the shredded cheddar. Once the puff pastry is baked, spread this filling over the center.

In a saucepan, melt the butter over medium heat and sauté the chopped asparagus for about 2 minutes. Add the diced ham and cook until browned, around 3-5 minutes. Scatter the mixture over the filling.

Create an egg wash by whisking an egg with a splash of water. Brush this over the pastry edges, then bake for another 10-12 minutes until set and golden. Let cool slightly before garnishing with thyme.