In a bowl combine the salt, pepper and garlic for the chicken seasoning.
Cut the chicken breast in half lengthwise, beat chicken until even in thickness and season on both sides.
In a large skillet, add the oil. Once hot, add the chicken. Sear two minutes per side then turn heat down to look and cook an additional 4-6 minutes until chicken is cooked through. Remove from skillet and cover to keep warm.
make sauce-
In the same skillet, add the butter, onion and mushrooms. Saute until onion is tender and mushrooms are golden brown.
Add the garlic and cook until fragrant.
Whisk in the flour quickly. Add the chicken broth, sour cream, Worshershire sauce andd quickly whisk to combine.
Turn the heat down to low and cook until the sauce thickens.
Add the chicken to the sauce and cook until chicken is reheated.