Cut the red bell peppers, drizzle with olive oil then roast them in a preheated oven at 200 degrees Celsius until the skin starts to darken.
In a pan, add the chopped garlic and onions with a drizzle of olive oil, and cook for 1 minute while frequently stirring.
Season with salt and black pepper.
Add the mushrooms and thyme and cook for 15-20 minutes until golden brown.
On a lightly floured surface, roll out the puff pastry and shape them into rectangles.
Spread pesto sauce on the puff pastry.
Top with 1 tbsp of the mushroom mixture and add a few strips of the roasted red pepper.
Brush the outer exposed edge of pastry with egg wash.
Bake the pastry for 15-18 minutes in a preheated oven at 180 degrees Celsius until the pastry is puffy and golden brown.
While the puffs are baking, cut the halloumi into cubes and fry in a pan until golden brown.
Once the pastries are baked, remove from the oven and top each with a few cubes of halloumi and serve warm.