Slice potatoes 1/8" thick. Put slices in a pot with cream, garlic and goat cheese. Season with salt and pepper. Place over medium heat. Bring to a simmer and cook 12-15 minutes until potatoes are very tender when poked with the tip of a knife. Transfer to a buttered 8" square baking dish. Bake at 375 for 20-25 min until golden brown.
Season both sides of steaks with salt and coarsely ground pepper. Place in a hot, dry skillet and cook 4-7 minutes on medium-high heat. Turn and finish cooking the other side.
Deglaze pan with wine, scraping up all the brown bits. Simmer until reduced and syrupy. Add capers and mustard, stirring in well.
Pour sauce over steaks and serve with gratin on the side.