Preheat oven to 425. Rinse chicken under cold water then pat dry with paper towels. Rinse finger potatoes and sit aside.
Season chicken inside and out with salt and pepper. Smear softened butter over entire chicken. Place breast side up in 13 x 9 inch (or larger) baking dish.
Insert 1/2 lemon into cavity along with 2 sprigs fresh rosemary and half head of garlic. Remove leaves off remaining sprigs of rosemary and sprinkle on top of chicken. Discard stems. Cover chicken with strips of bacon.
In gallon size storage bag add finger potatoes, extra virgin olive oil, salt and pepper and shake well to coat. Pour potatoes around chicken.
Cut the remaining 1 1/2 lemons into wedges and the remaining 2 garlic heads in half. Place lemon wedges and garlic halves around the chicken on top of the potatoes. Place in oven and bake for 1 hour uncovered.
Remove chicken from oven and remove bacon. Set bacon aside and return chicken to oven for an additional 30 minutes. While chicken is in the oven dice the bacon where it's completely cooked discarding the places on each piece where it's still raw and set aside. After 30 minutes check the chicken. Don't let the golden color of the chicken fool you into thinking it's done. Test chicken where the thigh meets the breast and see if the juices run clear. Remove chicken, garlic and lemon from baking dish to a large platter and tent with foil. Remove potatoes to a covered serving dish and keep warm.
While chicken is resting take 4 tablespoons of the pan drippings and place in saucepan. Add chicken broth and diced bacon and bring to a boil on medium high heat. Reduce by half (approx 6-8 minutes). If you need to thicken the gravy use the corn starch and ice cold water mixed together to make a slurry and add a little at a time checking for desired consistency.
Remove foil tent and slice chicken. Place on platter with roasted lemons and garlic heads. The garlic is soft and makes a nice spread to place on buttered crusty bread. Pour gravy into gravy boat (or bowl) and serve along side chicken and potatoes.