In a small bowl, or my preference, a two-cup glass measuring cup, whisk together the honey, spicy brown mustard, olive oil, and lemon juice.
Reserve ⅓ cup of the honey mustard and set it aside.
Cut the boneless skinless chicken into bite-sized pieces and place them in a gallon-sized Ziploc bag.
Pour the remaining honey mustard sauce over the chicken pieces.
Zip the bag shut and squish around to distribute the sauce.
Place in the fridge and let marinate for at least 2 hours, but it can be all day.
Even though you brown, crisp, and sauté' the ingredients in a skillet, you'll finish it off in a baking dish in the oven, so preheat your oven to 375 degrees.
Spray a 9x13 baking dish with non-stick cooking spray and set it aside.
Slice the bacon into pieces, slice up the mushrooms if necessary, and grate the cheese. Set these aside.
Take the marinated chicken from the fridge and drain the marinade off the chicken.
I just open a small end of the Ziploc zipper and squeeze the marinade out of the bag and down the kitchen sink drain.
Heat a large frying pan over medium-high heat until hot.
Drizzle in a couple of tablespoons of olive oil.
Add the chicken pieces to the hot pan. You don't want to crowd the pan, so you may need to do this step in two batches.
Cook chicken until it's browned on all sides and dump it into the prepared baking dish.
Use a spatula or something to distribute it in the dish evenly.
Drizzle the reserved honey mustard sauce over the pieces.
Place the frying pan back on the stovetop, add the sliced bacon, and cook until crispy.
Drain the bacon and sprinkle evenly over the chicken.
Return the frying pan to the heat again.
Drizzle in a little olive oil and add the mushroom slices.
Sauté' until they are half cooked.
Sprinkle the mushrooms over the layer of bacon.
Sprinkle the grated cheese over the mushrooms.
Put the baking dish in the oven and bake for 25 minutes at 375 degrees.
When done, allow this chicken dinner to cool for 10 minutes before sprinkling with green onions and serving.