Season the chicken with salt and pepper on both sides. Heat a large skillet over medium-high heat. Add the butter and olive oil. Add the chicken to the skillet and pan-sear until golden brown
Reduce heat to medium-low and add the red peppers and garlic to the skillet. Sauté for an additional 5 minutes, or until the peppers are crisp-tender.
In a mixing bowl, combine the chicken stock, peanut butter, soy sauce and red pepper flakes. Whisk until well incorporated.
Pour sauce into skillet. Bring to a boil over medium-high heat, then reduce heat to low and let simmer. Let simmer, stirring frequently for 5 minutes or until thickened.
Garnish the peanut chicken skillet with chopped green onions, crushed peanuts, and torn fresh cilantro before serving.