Preheat the oven: Start by setting your oven to 400°F (200°C). Line a baking sheet with parchment paper to prevent sticking and help with cleanup.
Prepare the chicken: Season the chicken breasts with salt, pepper, and dried thyme. Cook them in a skillet over medium heat for about 6-7 minutes on each side until they’re golden brown and fully cooked. Once they’ve cooled, shred them into bite-sized pieces.
Make the filling: In a bowl, combine the shredded chicken, mozzarella cheese, cheddar cheese, chopped onion, and minced garlic. Mix until everything is well combined and coated in cheesy goodness. Add salt and pepper to taste.
Prepare the puff pastry: Roll out the puff pastry on a floured surface. If using store-bought, you’ll have a large sheet—cut it into two equal rectangles. This will make it easier to handle and fold.
Assemble the jalousies: Spoon the chicken and cheese mixture onto one half of each pastry rectangle, leaving some room around the edges. Brush the edges with a bit of melted butter, then fold the other half of the pastry over the filling. Use a fork to press down on the edges, sealing them tightly.
Egg wash for golden perfection: Beat the egg and brush it over the top of the pastries. This will give your jalousies that beautiful, golden finish once baked.
Bake: Place the pastries on the baking sheet and bake them in the oven for 20-25 minutes, or until they’re puffed up and golden brown.
Serve and enjoy: Let the chicken and cheese jalousie cool for a couple of minutes before cutting into them. Serve warm, and enjoy every bite!