Dissolve yeast in warm water in medium bowl. Stir in remaining ingredients. Beat until smooth. Cover and let rise in warm place until double, 40 to 60 minutes. Grease griddle or heavy skillet and insides of four to six 3-inch flan rings or crumpet rings. (See NOTE). Place rings on griddle over medium heat until hot. Pour about 2 tablespoons batter into each ring. Cook until tops form bubbles and bottoms are golden brown, 1 to 2 minutes. Remove rings and turn crumpets to brown other side, 1 to 2 minutes. Repeat with remaining batter, greasing insides of rings each time. Serve with margarine or butter and jam or marmalade if desired. NOTE: 6 1/2 ounce tuna, minced clam or shrimp cans, tops and bottoms removed, can be substituted for the flan rings.