It’s hard not to love M&M cookies — easy, fun, and just plain yummy.

Years ago in a magazine was a recipe for “cookies by the stack” — a single cookie dough recipe that could be used with any number of mix-ins, from coconut flakes and chopped nuts to dried fruit or chocolate pieces. I glued the entire magazine page into my cookbook because it was so useful. I’ve made some of the variations on the page, but I use the recipe most often for chocolate chip cookies (see below).

These are going to taste good no matter what. It’s hard to mess them up! But if you want them to look good, too, there’s a trick: Mix only half of the M&Ms into the dough, and put the rest on by hand before they go in the oven. If you don’t, they won’t show up very well, as you can see here:

The cookies on the right had all the M&Ms mixed into the dough. The cookies on the left had only half mixed in, with the rest put on by hand.

The food scientist and cookbook author Shirley Corriher, in her terrific book “Cookwise: The Secrets of Cooking Revealed,” explains how shortening and butter can affect the spread of the dough and give you either a flat, crisp cookie or one that holds its shape. Butter melts over a narrow temperature range, so if you use all butter in the recipe, the cookies will spread soon after they go in the oven.

Shortening, on the other hand, stays the same texture over a wide temperature range, she says — so cookies made with part butter and part shortening will hold their shape better than if you use all butter. This recipe uses both in an equivalent ratio. Knowing the difference in fats, you can tweak the recipe how you like — if you want a crisper cookie, use more butter, for instance.

I mentioned chocolate chip cookies earlier. If you’d rather make those, just replace the 2 cups of M&Ms in this recipe with 2 cups of chocolate morsels (semi-sweet). Three other variations are below.

1/2 cup shortening
1/2 cup unsalted butter, softened
1 cup packed brown sugar
1/2 cup granulated sugar
1/2 tsp. baking soda
2 eggs
1 tsp. vanilla
2 1/2 cups all-purpose (plain) flour

Set oven to 375F (190C) degrees.

In a large mixing bowl, beat the shortening and butter with an electric mixer on medium to high speed for 30 seconds. Add the two sugars and baking soda and beat until fluffy.

Add eggs and vanilla and beat until combined. Stir in flour by hand, then add half the M&Ms.

Drop dough by slightly rounded tablespoons 2 inches apart on an ungreased cookie sheet, then place reserved M&Ms on top (crowd them together for best results). Bake 10-12 minutes or until the edges are light brown. Let cool on a wire rack.

*The dough can be kept for up to 24 hours in the refrigerator, or frozen for up to 6 months (thaw overnight before baking).

Variations:

PEANUT BUTTER-CHOCOLATE CHIP COOKIES
Replace the M&Ms with 1 cup peanut butter morsels and 1 cup semi-sweet chocolate morsels. Mix it all in the dough.

COCONUT-WALNUT COOKIES
Replace the M&Ms with 1 cup coconut flakes and 1 cup chopped walnuts.

FRUIT AND OATMEAL COOKIES
Substitute 1 cup rolled oats for 1 cup of the flour. Stir in 1 tsp. ground cinnamon into the flour mixture. Stir 6 oz. of dried fruit bits into the dough.