Season and Cook the Chicken:
Pat the chicken dry, then season with salt, pepper, garlic powder, and onion powder.
Heat butter or oil in a skillet over medium heat. Sear the chicken for 4-5 minutes on each side until golden brown. (For crockpot version, searing is optional.)
Prepare the Gravy:
In the same pan, add butter and sauté onions until soft. Add garlic and cook for 1 minute.
Stir in the flour and cook for 1 minute to form a roux.
Gradually whisk in the chicken broth, scraping up any browned bits from the pan.
Add thyme, rosemary, and cream (if using). Simmer until the gravy thickens.
Combine and Simmer:
Return the chicken to the pan, spoon gravy over the top, and simmer for 10-15 minutes until the chicken is cooked through.
For the crockpot method, pour the gravy over the chicken in the slow cooker and cook on low for 4-6 hours or high for 2-3 hours.
Serve:
Adjust seasoning if needed. Serve hot over mashed potatoes, rice, or biscuits.