Preheat oven to 425ºF. Cut a 24" sheet of foil. Thoroughly wash beets; cut stems and leaves 1" above beet crowns. Arrange beets on foil; securely seal ends to make a tight packet. Transfer packet to baking sheet. Bake for 1 1/2 hours, or until the beets are soft when pierced by a knife. Unwrap; let stand until cool enough to handle. Slip off skins; cut each beet into 8 wedges. Meanwhile, in large bowl, combine yogurt, sour cream, vinegar, mustard, salt and all-spice; stir in baked beets, apples and potato. To serve, line 4 plates with 2 lettuce leaves each. Arrange one-fourth of the beet mixture on each plate. Makes 4 servings