Cut the chicken into thin strips. Heat the butter in a large skillet over medium heat. Add the chicken and onion and cook until the chicken is no longer pink, about 5 minutes. Add the garlic, mushrooms, flour, paprika, salt and pepper; cook for 1 minute.
Add the broth and bring to a boil. Reduce heat to low and simmer for 10 minutes or until sauce thickens slightly. Remove from heat and stir in sour cream.