Preheat oven to 350 degrees.
In an enameled cast iron skillet, melt butter over medium-low heat. Add 1 tbsp. oil.
Add additional tbsp. oil to the skillet. Season chicken thighs with salt and pepper and add to the skillet, skin side down. Do NOT move the chicken until it is golden brown and EASILY and effortlessly lifts from the skillet. Flip and repeat browning. Remove chicken from the skillet and set aside.
Add carrots, celery, potato, onion, garlic, and mushrooms to the pan and saute/stir until the garlic is fragrant and the veggies are slightly browned.
Add soup and stock to the pan along with the thyme. Combine well with a wooden spoon.
Add the chicken back to the skillet. Add peas.
Add a pinch of salt and pepper.
Cover and cook in the oven for 30 minutes.
Uncover, place the biscuits evenly across the top of the chicken and veggies.
Return to oven and cook for 15 minutes, until biscuits are golden brown and the chicken and veggies are bubbling.
Serve each helping with a biscuit!