Use paper towels to pat dry the chicken thighs and then season with salt and pepper. Add 2 tablespoons butter and olive oil to large skillet and heat on medium high stove top. When butter and oil are hot, place chicken thighs in skillet, skin side down and sear for 10 minutes. Flip pieces and sear for 2 more minutes then remove from skillet and set aside.
Add remaining butter to skillet and over medium add onions and stir for about 5 minutes until softened. Add garlic and stir and sauté for another minute. Next, add broth and bourbon and simmer for 5 minutes and then add chicken back to skillet, skin side up. Simmer for another 25 minutes or until chicken is cooked through and sauce begins to thicken.
Add peas at the end, allow to simmer another minute or so and then garnish with parsley immediately before serving.
Using the same parts of the chicken helps to ensure cooking time will be the same for all of the pieces.
For food safety, always make sure chicken is cooked to an internal temperature of 165°.