Optional; fresh parsley for garnish
For the marinade; In a small bowl whisk together mustard, honey, mayonnaise, and lemon juice. Reserve ¼ cup sauce in a covered container and refrigerate until serving time.
Meanwhile, place the chicken breast in a large plastic zipper-top bag. Pour in remaining sauce and turn in bag until evenly coasted. Refrigerate 30 minutes or overnight.
To make the chicken; Turn griddle on low heat on one side and add bacon to cook. Remove onto paper towels until ready to use.
On the other side using medium heat add 2 tablespoons butter to melt and toss mushroom slices in the butter. You may want to slide into some of the bacon fat for flavor. Remove from heat once cooked.