Preheat oven to 375 degrees.
Trim excess fat off chicken breasts and slice in half, lengthwise, if chicken breasts are thick. If they're thin, cut breasts in half.
Pound chicken breasts to 1/4 inch thick using a rolling pin or mallet.
Pat chicken dry and season on both sides with garlic powder, salt and pepper.
Cook chicken in olive oil in a preheated pan set over medium heat for 3 minutes per side. You don't want them fully cooked, that will happen in the oven.
Place cooked chicken on a brimmed sheet pan.
Once all the chicken is done, in the same pan, cook one diced yellow onion for 10 minutes in the chicken drippings. Add more olive oil if needed.
Add minced garlic and cook 2 minutes more.
Add chicken stock and Better than Bouillon chicken base to the pan, stir and allow to thicken and reduce for 10-15 minutes.
Add heavy whipping cream, salt, pepper and ground thyme, stir and allow to thicken 10 minutes.
Pour the sauce over the chicken in the sheet pan. Spoon sauce over each piece of chicken.
Bake uncovered for 15 minutes.
Serve hot!