In a large pot of salted boiling water, cook cauliflower until very soft, about 10 to 15 minutes. Drain and pat dry. In a mixing bowl, mash cauliflower to small bits. Add mashed potatoes, matzoh meal, garlic, salt, pepper, and egg, and blend thoroughly. Shape into 12 patties 3 inches in diameter and about 1/2 inch thick. Sprinkle with kasha, pressing into both sides. Melt 3 tablespoons butter/margarine in a large skillet over medium-high heat. Fry latkes, adding more butter/margarine as necessary, until they are browned and crust is crisp, about 3 minutes per side. Drain on paper towels. Serve hot.