In a small bowl, add all the ingredients to the chipotle mayo. Use an immersion blender to blend all the ingredients together until the mayo is thickened and smooth.
In a cast iron skillet or frying pan, cook bacon to desired crispness. Reserve the fat, if desired. Set the bacon on a wire rack or paper lined plate to drain.
Season chicken breasts with salt and pepper on both sides. In the cast iron skillet or frying pan, heat a tablespoon of high-heat oil over medium high heat. Cook chicken breasts, 3 minutes on both sides, or until chicken is cooked through. Set aside on a plate to rest for 3-5 minutes. Slice the cooked chicken breasts to prep for the sandwiches.
Preheat your panini press to medium high heat. Spread softened butter or residual bacon fat over one side of each piece of bread, then spread a spoonful of chipotle aioli over the other side of the slices of bread. Stack bacon, chicken, tomato, cheese, and on the aioli side of 4 slices of bread, then top with the other slice.
Press in panini press for 5 minutes, until cheese is melted and bread is well toasted.
Cut the sandwiches in half and serve immediately.
