Chop the chicken breasts into bite-sized pieces. Season them generously with salt and pepper. Set aside.
Preheat the oven to 350 degrees.
Heat a large ovenproof skillet on the stove over medium heat. Chop the bacon into medium-sized pieces. Once the skillet is heated, add the bacon and stir.
Sauté the bacon until it's cooked through, about 5-7 minutes. Remove the bacon from the skillet using a slotted spoon and drain on paper towels. Reserve the remaining bacon grease in the pan.
Add a little additional cooking oil to the pan if you don't have enough bacon grease left over to coat the bottom of the skillet. Add the chicken pieces to the skillet in batches and brown on all sides, about 1-2 minutes per side. Remove the browned chicken pieces from the pan and set aside.
Add more oil to the skillet if needed. Toss in the diced mushrooms. Once they start to release their juice, sprinkle them with salt and pepper.
Add the chicken back to the skillet and continue cooking until chicken is no longer pink, about 5-7 minutes.
Remove the skillet from the heat, stir in the reserved bacon. Sprinkle everything with shredded cheddar cheese.
Place the skillet in the oven for about 2-3 minutes until the cheese is melted. Garnish with diced green onions before serving.