Preheat your oven to 375°F (190°C).

In a skillet over medium heat, add a drizzle of olive oil. Sauté finely chopped onion and minced garlic until translucent, about 3-4 minutes.

Add the chopped mushrooms and cook until they soften and release moisture, roughly 5-7 minutes. Stir in fresh spinach until wilted, about 2-3 minutes. Season with salt and pepper to taste, then set aside to cool slightly.

Transfer the cooled mixture to a mixing bowl. Fold in cream cheese and shredded cheese until combined.

Roll out the puff pastry sheets on a lightly floured surface. Cut into squares, approximately 3x3 inches.

Spoon the filling onto the center of each pastry square. Fold over into triangles and press edges to seal.

Whisk the egg for egg wash and brush the tops of the pastries. Skip this for a vegan version.

Arrange pastries on a baking sheet and bake for 20–25 minutes, until puffed and golden brown.

Let cool for about 10 minutes, then serve warm, optionally with dipping sauce.