In a small bowl, combine the flour, baking powder and salt. In a 1-qt. glass jar, layer the flour mixture, brown sugar and M&M's. Cover and store in a cool dry place for up to 3 months. Yield: 1 batch (about 4 cups mix).
To prepare muffins: Place muffin mix in a large bowl. Whisk the bananas, butter, eggs and vanilla; stir into dry ingredients just until moistened. Fill greased or paper-lined miniature muffin cups three-fourths full. Bake at 400° for 9-10 minutes or until a toothpick comes out clean. Serve warm. Yield: 4 dozen.