Heat butter in a large skillet over medium-high heat until foaming subsides. Season chicken pieces generously with salt and pepper, then sear until golden brown on all sides, approximately 6-8 minutes total. Don't move the chicken too frequently—let it develop a beautiful crust because this adds tremendous flavor to the warm dinner.

Remove chicken from the skillet and set aside on a clean plate. Add diced onion to the same skillet and sauté for 3-4 minutes until softened and fragrant. Stir in minced garlic and cook an additional 30 seconds, stirring constantly to prevent burning.

Add sliced mushrooms to the skillet and cook for 5 minutes, stirring occasionally, until they release their moisture and begin to golden. Pour in chicken broth, scraping up any browned bits from the bottom because these bits add deep umami to this cozy creamy chicken dinner recipe.

Return the seared chicken to the skillet along with thyme and rosemary. Reduce heat to medium and simmer for 15-18 minutes until the chicken reaches 165°F internally. While the chicken simmers, cook egg noodles according to package directions in a separate pot, then drain and set aside.

Whisk cornstarch with water in a small bowl to create a smooth slurry. Stir this mixture into the simmering chicken, then add heavy cream and cook for 2 minutes until the sauce thickens noticeably. The sauce should coat the back of a spoon when ready.

Fold in cooked egg noodles and frozen peas, stirring gently to combine everything. Taste the dish and adjust seasoning with additional salt and pepper as needed. Simmer for 1-2 minutes until peas heat through, then remove from heat and garnish with fresh parsley before serving.