Preheat the oven to 350 degrees F (175 degrees C). Line a baking sheet and a baking pan with aluminum foil.

Arrange bacon slices on the prepared baking sheet in a single layer.

Cook in the preheated oven until browned and crisp, about 15 minutes. Drain bacon on a paper towel-lined plate, then chop. Keep the oven on.

Slice chicken breasts horizontally, without going all the way through. Set aside.

Combine cream cheese, 1/4 cup Cheddar cheese, green onions, cilantro, and garlic in a bowl; stir in chopped bacon to combine.

Open chicken breasts at hinge points (like a book); spread cream cheese mixture in a thin layer over each breast. Close breasts; transfer to the prepared baking pan.

Bake in the preheated oven for 30 minutes. Top stuffed chicken breasts with remaining 1/2 cup cheese; continue baking until chicken is no longer pink in centers and the juices run clear, about 10 minutes more. An instant-read thermometer inserted into centers should read at least 165 degrees F (74 degrees C). Cool slightly before serving.