Coat chops with flour. Brown with garlic in 2 tablespoons oil. Season with salt and pepper. Place potatoes in the bottom of baking dish large enough to hold chops without crowding. Place chops on top. Separate onion slices into rings; place over chops. Combine sour cream and dry mustard, pour over all. Cover pan with foil and bake at 350F for 1 1/2 hours. Remove foil from pan and bake a little longer until top is nicely browned.