Start by cutting the top of the bell pepper and remove their core.
Next, make small cuts along the side of each pepper.
In a large skillet over medium to low heat add a drizzle of olive oil, the onion cut into small cubes, the red bell pepper cut into small cubes and sauté until lightly golden brown.
Add the ground beef and sauté until golden brown.
Season with the salt, a pinch of black pepper and mix everything together to combine.
Turn off the heat, add parsley to taste and mix once more.
Once you've done that, cut the puff pastry into round slices using a glass or a round pastry cutter.
Now, on top of each of these slices, add 2 tablespoons of the meat mixture we prepared, 1 cube of mozzarella cheese and close the pastries by shaping them into balls.
In a large baking tray, add the peppers we hollowed out earlier and stuff each pepper with one of the pastry balls we prepared.
Brush the egg all over the pastries and score the top of these pastries.
Take the baking tray to a preheated oven at 180 ° C (350 ° F) and let everything bake for 25 minutes.
Serve.