In a medium sized bowl, combine honey, mayonnaise, Dijon mustard, whole grain mustard, yellow mustard, garlic powder and kosher salt. 

Whisk to combine. This is your marinade for your chicken as well as your sauce to drizzle on later so pour half of it into a container and place in the fridge to use after everything is cooked. 

If your chicken breasts are really thick, or if any of them are much bigger than the others, I like to pound them all to about the same thickness. This just makes it so they will cook evenly. The best time to do this is before the marinade, so check this now. If you have never pounded chicken, you will just need plastic wrap and something heavy and flat like a kitchen mallet or you can even use a small skillet. Surround the chicken on bottom and top with plastic wrap and you can pound with your heavy object. The goal is just to get all your pieces consistently thick so they will cook similarly. 

Place your chicken into the bowl with the remainder of the marinade. Cover bowl and place in the fridge for 1 to 2 hours to marinate. 

When the chicken is nearing the end of the marinade time and you're ready to cook, pre-heat your oven to 400 F (200 C). 

Put a medium sized skillet over medium heat and add your six strips of bacon. I usually cut each strip in half to make them easier to cook and also a better size for placing on top of the cooked chicken. 

Cook the bacon until it's browned and crispy, probably about 10 minutes. 

Drain off all the bacon grease from the pan (save or discard grease) and place the bacon on a paper towel lined plate to use later. 

Add two tablespoons of butter to the pan and bring it back to medium heat. 

Once the butter is bubbly, add all of your sliced mushrooms and cook for 8 to 10 minutes, until the mushrooms are tender. You should season your mushrooms lightly with salt and pepper while they cook. 

Remove the mushrooms to a bowl for use later. 

In that same medium skillet or a grill pan (or your outdoor grill) over medium high heat, add your chicken that you have removed from the marinade. 

Grill the chicken for four minutes per side. Your goal at this point is to almost fully cook the chicken, it will finish cooking in the oven. This keeps the chicken moist and doesn't overcook it. 

When the chicken is done, remove it from the pan and add it in a single layer to an oven safe casserole dish or baking pan. 

On top of each piece of chicken, add one spoonful of honey mustard marinade, then top that with some cooked mushrooms and place two half bacon pieces on top of each piece of chicken. 

Sprinkle/spread shredded Monterey Jack and Cheddar cheese evenly on top of each piece of chicken.

Bake in the oven for 10 minutes.

Garnish each piece of chicken with chopped parsley and serve with honey mustard on the side.