Use an electric mixer to combine the Dijon mustard, honey, vegetable oil, and lemon juice in a small bowl. Whip the mixture for about 30 seconds.
Pour about 2/3 of marinade over the chicken breast and marinate them, covered, in the refrigerator for about 2 hours. Chill the remaining marinade until later.
After chicken has marinated, preheat oven to 375º and heat a large frying pan and t tbsp of oil. Sear the chicken in the pan for 3-4 minutes each side or until golden brown. Remove the pan from the heat, but keep the chicken in the pan. (if you don't have an oven proof pan, heat a baking dish in preheating oven)
As chicken is cooking, in a small frying pan saute the sliced mushrooms in the butter.
Spray baking dish and transfer the chicken unless you have used an oven safe pan. Brush each seared chicken breast with a little of the reserved honey mustard marinade (NOT the portion that the chicken soaked in), being sure to save a little extra that you can serve on the side later with the dish. (I like to make a second batch of the marinade because I love it!)
Season the chicken with salt, pepper, and a dash of paprika.
Stack two pieces of cooked bacon, crosswise, on each chicken breast.
Spoon the sauteed mushrooms onto the bacon, being sure to coat each breast evenly.
Spread 1/4 c of MJ cheese onto each breast followed by 1/4 c of Cheddar.
Bake the pan of prepared chicken breasts for 10-15 minutes or until the cheese is thoroughly melted an starting to bubble.
Sprinkle with parsley if desired. Put extra honey mustard marinade into a small bowl and serve on the side.