Peel apple, quarter, and remove core. Cut into 1/2" dice. Mince garlic. Stem oregano and coarsely chop. Pat chicken breasts dry, and season both sides with a pinch of salt and pepper.

Place a medium non-stick pan over medium-high heat and add 2 tsp. olive oil. Add butternut squash, apple, and half the garlic (reserve remaining for sauce) to hot pan and stir occasionally until lightly browned, 4-6 minutes. Remove from burner and toss with half the oregano, half the butter (reserve remaining of both for sauce), 1/4 tsp. salt and a pinch of pepper. Transfer vegetables to prepared casserole dish (you may also use two small ramekins). Wipe pan clean and reserve.

Return pan used to cook vegetables to medium-high heat and add 1 tsp. olive oil. Add chicken breasts to hot pan and sear until golden brown, 4-5 minutes per side. Transfer chicken to a plate. Chicken will finish cooking in a later step.Reserve pan; no need to wipe clean.

Top vegetables in casserole dish with goat cheese and roast until squash tender and cheese is lightly melted, 8-10 minutes. While gratin cooks, make sauce.

Return pan used to cook chicken to medium-high heat. Add 1/2 tsp. olive oil and remaining garlic and cook until aromatic, 30-60 seconds. Add 1/2 cup water, brown sugar, remaining oregano, chipotle powder (to taste- it's quite spicy) and chicken and any accumulated juices to pan. Flip chicken occasionally until sauce is thick enough to coat the back of a spoon and chicken reaches a minimum internal temperature of 165 degrees, 3-5 minutes. Remove from burner and swirl in butter. Place chicken on a plate and place gratin next to chicken. Top chicken with sauce.