Mash the avocado and add ranch dressing. Blend with a hand mixer until smooth. Set aside.
Preheat oven to 350 degrees F. Line a 13x9 inch sheet pan with tin foil (for easy clean up). Place a wire cookie rack over the sheet pan and lay out the strips of bacon in one layer. The bacon strips should not overlap each other. In a small bowl, mix the brown sugar, maple syrup and rice vinegar together. After 10 minutes, remove the bacon back in the oven and repeat three times, every 5 minutes. The third time after brushing on the brown sugar mixture, use pepper mill to lightly sprinkle cracked black pepper onto the bacon (optional). Then remove bacon from oven and allow to cool.
Cut chicken breasts in half lengthwise. If the breasts are thick, pound to uniform thickness ( ½ - ¾ inches). Fry the chicken in oil and set aside to cool. When the chicken is cool, cut into thin strips.
Spread one side of each bread slice with butter. Place bread slice, buttered side down on the panini grill. Spread spicy brown mustard, top with chicken, 2 cheese squares, tomatoes, and bacon. Finish with spreading avocado mixture on the bottom of the top slice (which has been buttered on top). Cook on panini grill until the bread is golden brown and the cheese is melted.
If you do not have a panini press, you can use cast iron pans and place another cast iron pan on top of the sandwich, turning the sandwich over after 4-5 minutes to cook on the other side.