Cook the bacon in a heavy-bottomed cast iron skillet (or an oven-proof pan), until it's crispy. Remove bacon from the pan and transfer to a paper towel-lined plate to drain.
In a mixing bowl, combine the cream cheese, 3/4 cup of mozzarella cheese, garlic powder, diced jalapenos, and 3/4 of the cooked bacon.
Cut the chicken breasts in half to butterfly them open. (Do NOT cut all the way through!) Sprinkle lightly with salt and pepper. Divide the filling between the chicken breasts and spread over one side of the breast. Then secure them closed with toothpicks.
Drain all but 1 tablespoon of bacon fat from the skillet and put it back over medium-high heat. Cook the chicken for about three minutes on each side. (If you don't have an oven-proof skillet, transfer the chicken to a baking dish now.)
Sprinkle the remaining shredded mozzarella and bacon over each chicken breast. Add some jalapeno slices on top too.
Place the skillet in the oven and bake for 15 to 20 minutes or until the thickest part of the chicken reads 165 degrees F internal temperature.