To get a head start on this recipe, prepare the turkey as directed in Step 1. Place turkey in a zip-top plastic freezer bag, and chill 24 hours.
Cut turkey into 1/2-inch slices. Place medaillons between 2 sheets of heavy-duty plastic wrap, and flatten to 1/8-inch thickness, using a rolling pin or flat side of a meat mallet.
Melt 2 Tbsp. butter in a large skillet over medium-high heat. Add turkey; cook, in batches, 2 to 3 minutes on each side or until lightly browned. Remove turkey from skillet, and keep warm. Reduce heat to medium.
Melt remaining 3 Tbsp. butter with garlic in skillet over medium heat; cook 1 minute or until lightly browned. Stir in cream and next 3 ingredients. Bring to a boil, and cook, stirring occasionally, 10 to 12 minutes or until reduced by half. Stir in cheese. Spoon sauce over turkey. Sprinkle with parsley, and serve immediately.