If you are using boneless turkey breast, you can cook that ahead of time in a slow cooker for 4-6 hours on medium heat. Once the turkey breast is cooked through and tender, shred the turkey into thin strips and prepare the sandwiches. If you do not have a boneless turkey breast to cook you can use sliced turkey lunchmeat instead.
Layer the sandwiches with bread slices that have been spread with mayonnaise on one side and sweet chili sauce on the other. Place a slice of gouda cheese on both sides of the bread. Add plenty of turkey in the center of the sandwich and sliced avocados. Close the sandwich grill on a panini grill or flat griddle until golden brown and the cheese has melted. Use butter to help the bread get nice and golden brown and crispy. Serve warm.