In 10-inch skillet, heat a few teaspoons of the olive oil over medium-high heat until hot. Add chicken, salt, pepper and red pepper flakes. Cook until golden on outsides and no longer pink in center. Remove chicken to plate. Add onion to the still-hot pan; season with salt, and cook until onion begins to soften and become translucent. Add garlic; cook 60 seconds. Add 2 tablespoons of the olive oil, followed by flour, and stir to make a roux. Cook the roux 1 to 2 minutes or until lightly golden. Gradually beat in the chicken broth with whisk, followed by the milk, and simmer until slightly thickened into a gravy.