Cook bacon in a medium skillet set over medium heat until the bacon is crispy and the onion is tender, about 3 minutes. Remove to a plate and set aside. Sprinkle both sides of the chicken with ranch seasoning, and add to the skillet. Brown the chicken on each side, about 3 minutes each. Remove chicken to plate with bacon and onions.
Stir in the half and half, salt and pepper. Break the spaghetti noodles into bite sized pieces and add to the skillet. Stir to combine. Nestle the chicken into the spaghetti and top with the spinach. Reduce the heat to simmer, cover the skillet and cook until the sauce has thickened, the noodles are tender and the chicken has cooked through, about 20 minutes.
Remove the skillet from the heat. Add the bacon and onion back to the skillet and grate Parmesan cheese over top of the chicken and pasta and serve.