IN A LARGE saucepan of boiling salted water, cook potatoes until tender (10 minutes) DRAIN and let cool PAT dry. TO MAKE AHEAD REFRIGERATE POTATOES IN AIRTIGHT CONTAINER FOR UP TO 24 HOURS ON CUTTING BOARD and using heavy saucepan, gently smash each potatoe to about 1/2 inch thickness. ARRANGE on greased baking sheet. BRUSH with oil SPRINKLE with salt and pepper. ROAST in 425 oven until crispy and edges browned, turning halfway through (about 35 minutes) ARRANGE on platter. W A R M D R E S S I N G In small saucepan, heat oil over medium heat. COOK garlic until light brown (5 minutes) STIR in capers, cook 1 minute. STIR in 2 tablespoons parsley and sherry. COOK 30 seconds. SPOON over potatoes. SPRINKLE with remaining parsley.