Banana Chocolate Chip Muffins

1/2 cup softened margarine or butter 1 3/4 cup sugar 3 cups mashed RIPE bananas 1 egg 1 Tbsp vanilla 1 cup bran flakes 2 cups flour 1 tsp salt 1 tsp baking soda 1/2 cup plain yogurt 1/2 bag mini semi-sweet choc chips chopped nuts (optional)

Cream margarine. Add sugar gradually. Add vanilla, egg and bananas. Mix well. Mix soda and salt with flour. Add flour slowly into banana mixture alternately with yogurt. Mix well. Add bran flakes and mix well. Add in choc chips Mix lightly. Use paper baking cups - fill 3/4 full. Bake 350° for 25 to 30 minutes.