Dredge the chicken cutlets in flour, seasoned with salt, pepper, and garlic powder.
In a skillet, heat olive oil and 2 tablespoons of butter over medium heat. Sauté the chicken cutlets until golden brown and cooked through.
Remove the chicken and add the remaining butter, garlic, shallots, and mushrooms to the skillet. Sauté until mushrooms are tender.
Add grape juice, chicken broth, and thyme. Bring to a simmer.
Stir in heavy cream and Dijon mustard. Thicken the sauce with dissolved cornstarch.
Return the chicken to the skillet and coat with the sauce. Serve warm.