Season the chicken breasts with salt, pepper, garlic powder, and onion powder.
In a large skillet, heat the olive oil over medium-high heat. Sear the chicken breasts for 2-3 minutes on each side until golden brown.
Place the seared chicken breasts in the slow cooker.
In a bowl, mix together the chicken broth, cream of chicken soup, and Worcestershire sauce. Pour this mixture over the chicken in the slow cooker.
If using, add the sliced mushrooms, chopped onions, and frozen peas on top of the chicken.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender.
Once done, shred the chicken with two forks and stir the gravy to combine.
Serve over rice, mashed potatoes, or noodles.