In a small bowl, combine cornstarch and cold water. Mix well.
In a large nonstick skillet, heat oil over medium heat. Add chicken; cook, turning once, until golden, about 6 minutes. Add garlic and pepper; cook for 1 minute. Place chicken in a 13-x-9-inch baking dish.
Add wine, mushrooms, green onion, thyme and paprika to skillet. Cook over high heat, stirring, until liquid is reduced by half, about 5 minutes.
Add cornstarch mixture to skillet. Cook, stirring constantly, until thickened, about 3 minutes. Pour sauce over chicken in dish. Cover with foil and bake until chicken is cooked through and no longer pink, about 15 minutes.