Preheat the oven to 400 degrees Fahrenheit and spray a 9x13 inch baking pan or casserole dish with nonstick spray and set aside.

Add the mayonnaise, sour cream, garlic, olive oil, and ranch seasoning to a medium bowl and stir to combine.

Stir in ¾ of the bacon, ¾ of the cheddar cheese, ¾ of the mozzarella cheese and all the onion then set aside.

Place one of the chicken breasts onto a plate and cut deep holes into it using a knife then spread the ranch mixture onto the chicken and push some of it into the holes.

Place the chicken breast into the baking pan and repeat the process with the remaining chicken breasts and ranch mix.

Sprinkle on the remaining cheddar cheese, mozzarella cheese and bacon then loosely cover the pan with part aluminum foil.

Bake for 20 minutes then remove the aluminum foil and bake for another 10 minutes or until the cheese starts to bubble around the edges and turn a light golden color.

Let the chicken rest for 10 minutes before serving with freshly chopped chives and additional bacon for garnish if desired.