Peel the onion, then slice it into thin strips. Rinse the tomato and the lettuce leaves. Slice the tomato into rounds and set everything aside.
Prepare the breading for the chicken. In a first shallow dish, beat the eggs. Pour the breadcrumbs into a second dish and add the roast chicken and poultry mixture.
Dip the chicken fillets in the beaten eggs, then coat them with breadcrumbs. Season with salt and pepper.
Heat a drizzle of olive oil in a skillet. Add the chicken fillets and cook them for about 5 minutes on each side. The breading should turn a nice golden color and become crispy.
Warm the burger buns for a few minutes, then spread a thin layer of ketchup or mayonnaise on the bottom half.
Assemble the burgers by topping the buns with the chicken fillets, cheese, lettuce, a few slices of tomato, and red onion rings.
