In a sealable plastic bag or coverable bowl combine 1/3 cup Dijon mustard, vinegar, honey, lemon juice, thyme, paprika, pepper, and salt. Add the chicken breast.
Seal or cover and place into the refrigerator and allow to marinate for 1 hour.
Add the bacon strips into a large skillet. Heat the pan to medium heat and cook the bacon until crispy. Transfer to a plate lined with paper towels.
Lightly grease the grates of an outdoor grill. Heat the grill to medium-high heat. Remove the chicken breast from the marinade.
Place the chicken breast onto the grill and cook for 10-15 minutes per side or until the chicken is fully cooked (the internal temperature has reached 165 Degrees F.). Remove from the grill and allow to cool for 10 minutes. Slice the chicken breast into strips.
Butter one side of each slice of bread. Take one of the bread slices butter side down and spread a layer of Dijon mustard onto the top. Place 1 slice of cheese on top of the mustard. Layer on half of the chicken and half of the bacon. Top with an additional slice of cheese. Place the other bread slice over the cheese, butter side up. Repeat with a remaining sandwich.
Heat a large skillet or griddle to medium-high heat. Add the sandwiches to the skillet butter-side down.
Cook until the sandwiches are golden brown on the bottom (about 2 minutes). Turn and cook for another 2 minutes on the other side. Cook until golden brown and the cheese has melted.