To prepare sauce – Heat butter in medium sized saucepan over medium-high heat. Add shallots, thyme, salt and pepper. Cook for 3-5 minutes until shallots are softened. Add brandy. Let cook 2 minutes. Add chicken broth, cream and Dijon mustard and cook for 15 minutes, letting sauce reduce slightly. In a small bowl, whisk together flour and water until smooth. Whisk flour/water mixture into sauce and cook for an additional 5 minutes. Set aside.
Season chicken breasts with salt and pepper. Heat olive oil in large non-stick frypan. Add chicken breasts and cook for about 5 minutes on each side until cooked through. Add grapes to pan and cook for 3 more minutes. Add sauce to pan and swirl to coat chicken breasts. Serve chicken breasts with grapes and sauce spooned over them.