In a bowl, combine sauce ingredients. Place in refrigerator to chill. Prepare grill or griddle. Boil potato in water over medium heat until tender, about 10 min. Meanwhile, combine remaining ingredients in a medium bowl. Drain potato and mash with a fork or masher. Add potato to bowl, mix well and form into 4 thin patties. If potato mixture is too dry to hold together, add a little water before making patties. Grill patties 4 to 5 min. on each side until lightly browned. Serve on hamburger buns with sauce and your choice of fixings. I don't have a grill so I broiled mine instead and they turned out great! Brown and crispy! These have a nice taste. From my "Best of Vegetarian Times" collection.