I do the same -- Tollhouse recipe and substitute M&Ms for the chips. I prefer to use the mini-M&Ms, if I can find them. If not, the regular ones work fine. At Christmas time, I get the bags that are just red and green. And get extra bags, if you can. After the holiday, separate them in to all red and all green. Red for Valentine's Day (either in cookies or the candy dish) and green for St. Patrick's day cookies or candy dish.