In a skillet, melt butter on medium heat. Add onion and sliced mushrooms.

Cook until tender.

Add the spinach, salt, and pepper, and stir until cooked and wilted. Remove from the heat and let it cool to room temperature.

Put the mushroom and spinach mixture in a food processor and pulse, so it is evenly minced but not overly processed.

Holding the knife horizontally, insert it into the thick end of each chicken breast and cut to make a deep pocket. Be careful not to pierce through the other end.

Spoon the mushroom and spinach mixture evenly into the pockets of each chicken breast.

Wrap each stuffed chicken breast with two slices of bacon. Place on the smoker rack.

Set the smoker to 250ºF using Bradley Premium Sage Bisquettes (or Hickory Bisquettes).

Smoke the chicken until they reach an internal temperature of 165ºF.