Begin by slicing the boneless, skinless chicken breasts horizontally to create four thin cutlets. Place the cutlets in a bowl and drizzle with olive oil.

Sprinkle paprika, salt, black pepper, and optional chili flakes over the chicken cutlets. Allow the seasoned chicken to rest for about 10 minutes.

Preheat your grill or grill pan to medium-high heat. Grill each side of the seasoned chicken cutlets for 3-4 minutes or until cooked through.

Melt 4 tablespoons of unsalted butter in a small saucepan over low heat. Add minced garlic and chopped parsley, stirring until fragrant.

Brush thick-cut sourdough bread slices with prepared garlic butter. Toast in a skillet until golden brown and crispy, around 3-4 minutes.

In a small bowl, combine mayonnaise, Dijon mustard, and lemon juice until smooth. Set aside.

Spread a layer of the lemon-Dijon mayo on one side of each toasted bread slice. Layer fresh lettuce, grilled chicken cutlet, and tomato slices.

Gently press the sandwich together and serve warm.