Beef with mushroom

3 teaspoons unsalted butter or 3 teaspoons unsalted margarine 1 large onion , finely sliced 3/4 lb button mushroom , sliced 1 garlic clove , minced 1 cup[...]

5 ounce 95% lean grnd beef 1 tsp fat-free lowfat sour cream 1 tsp thyme 2 tsp grated onion 1/4 tsp salt 1/8 tsp freshly grnd black pepper 1 x english muffins[...]