Begin your Chicken Avocado Melt Sandwich by seasoning the boneless skinless chicken breasts with salt and pepper. Preheat a skillet over medium-high heat.

Add a drizzle of olive oil into the preheated skillet, then place the chicken breasts in the pan and cook for 6-7 minutes on each side until golden brown. Remove and let rest.

While the chicken is resting, slice the avocado, red onion, and tomato into thin pieces, and prepare your cheese.

Spread mayonnaise and Dijon mustard on two slices of your chosen bread. Layer with the chicken, avocado, cheese, red onion, and tomato, then cap it with another slice of bread.

Heat a skillet or grill pan over medium heat and add butter or olive oil. Grill the sandwiches for 3-4 minutes on each side until golden brown and the cheese melts.

Once grilled, remove the sandwiches from the skillet, allow them to cool slightly, then slice in half and serve immediately.