In a shallow bowl, combine the flour, salt, pepper, and garlic powder. Mix to incorporate. Set aside.
Add the 3 TBL of Olive oil to a large skillet. Heat over medium-high heat.
While the skillet is heating, dredge the chicken in the flour mixture-shaking off any excess flour.
Add the chicken to the pan skin side up. Fry for 4-5 minutes. Turn the chicken over, putting the skin side down.
Cover the skillet and continue frying the meat. I found that this helps the meat cook evenly, faster and still retains the crispy skin. Cook another 4-5 minutes. Temp the legs and wings, if they are done, remove them from the pan and continue cooking the breast and thigh until it reaches 165 degrees.
Remove the chicken and let rest on a plate. Cover to keep warm
To the skillet, add the sliced mushrooms and cook until they are well-browned on both sides.
Add the butter, onions and garlic to the pan and cook until softened and fragrant-about 30 seconds.
Add the chicken broth and wine; scrape the pan to get all the good bits into the sauce. Add the mustard and bring the sauce to a boil.
In a cup, add the cold water and cornstarch. Mix to make sure it is smooth and incorporated. Pour into the sauce and stir in. Continue cooking another minute or two.
Add the cream bring back to a simmer, add the chicken pieces back in (or not...because the chicken is completely cooked and crispy). Simmer a few minutes until the sauce is thickening.