Cook the Chicken
Season chicken breasts with olive oil, salt, pepper, and smoked paprika.
Heat a skillet over medium-high heat and cook chicken for 4-5 minutes per side, until golden brown and fully cooked.
Let the chicken rest for 5 minutes, then slice thinly.
Assemble the Sandwich
Spread mayonnaise and Dijon mustard on one side of each slice of bread.
Layer cheese, sliced chicken, avocado, tomato, and red onion.
Top with another slice of cheese and close the sandwich.
Grill to Perfection
Heat butter or olive oil in a pan over medium heat.
Place the sandwich in the pan and cook for 3-4 minutes per side, pressing down slightly.
Flip carefully and cook until golden brown and the cheese is melted.
Serve & Enjoy
Let the sandwich cool for a minute before slicing.
Serve warm with your favorite dipping sauce or side.