Toast the bread slices lightly in a toaster or pan.

In a pan, melt 1 tbsp butter and add 3 pinches of salt and 1 tbsp minced garlic.

Slice the onions and sauté them in the pan until caramelized (brown and soft).

Slice the store-bought chicken breast thinly and lightly grill it in the same pan.

Prepare the aioli sauce by mixing 2 tbsp mayonnaise, 1 tbsp mustard, and 0.5 tbsp minced garlic.

Spread the aioli sauce on one side of the toasted bread slices.

Layer the grilled chicken breast, caramelized onions, and optional bell pepper slices on the bread.

Top with mozzarella cheese and optional cheddar cheese, then bake at 180°C for 5 minutes or microwave for 1 minute.