Place the mackerel into a bowl and crush with a fork. Finely chop the red peppers, chilies, and onion. Mix with the fish. Crack the egg into a bowl and whisk. Add half the egg to the fish and mix, seasoning with salt, pepper and savory.
Cut the puff pastry into triangles. Place a little stuffing in the wider part of the triangle and from there, roll the croissants. Spread baking paper on a baking tray and place the croissants on it. Grease them with the rest of the egg. Bake at 180 ° C (top-down) for about 20-25 minutes until golden brown.