Updated January 2, 2021.

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These cookies are a great way to use leftover Halloween candy. I had a mixture of fun size Snickers, Milky Way, and 3 Musketeers bars. I don’t typically eat Snickers on their own, but I thought the bars would all make a nice cookie. These cookies did not disappoint! Their softness and fluffiness rival my Soft Snickerdoodle Cookies. They also stayed soft after several days.

What makes these soft cookies soft?

Short answer: baking science!

These cookies use all brown sugar. Brown sugar retains more moisture during baking than white sugar. Brown sugar is more acidic than white sugar, which helps the eggs solidify faster during baking and slows spreading. The egg also contributes to moisture and structure. (See How To Make Soft or Crispy Cookies by The Spruce Eats and Cookie Chemistry by King Arthur Flour.)

Most of my cookie recipes (such as my Fruitcake Cookies and Spiced Pecan Chocolate Chip Cookies) use one teaspoon of baking soda, but I increased the amount by a quarter teaspoon for this recipe. I think that contributed to some additional rise and fluffiness.

What’s interesting about these cookies is that the dough is not chilled. Generally, chilled cookie dough will spread slower during baking and will be softer. I haven’t made this exact cookie recipe with chilled dough to test the difference between chilling versus not.

It’s also important to cream the butter and sugar well in the beginning. I gave it a solid two minutes until it got really light and fluffy. This aerates to create lightness. (When I was a kid, I hated “the butter and sugar part” of baking. I used to have to cream the butter and sugar by hand with a wooden spoon. I guess Mom didn’t trust me with kitchen electrics, probably for good reason!)

The candy bar ingredients could also create some benefits for softness in these cookies, but I’m not totally sure. I plan to test this recipe with basic chocolate chip cookies soon and compare the results to these.

Continue reading after the recipe card for step-by-step photos, notes, and answers to common cookie-baking questions.

Step-By-Step Photos & Recipe Notes

Preheat oven to 350°. Chop the candy bars into small pieces until you have about two cups worth. I chose Snickers, Milky Way, and 3 Musketeers for these. If you don’t have enough chocolate bar pieces, you can supplement with chocolate chips, M&Ms, or chocolate chunks.

Microwave butter (1 cup, or 2 sticks) for 45 seconds (it will be partially melted).

Why did I microwave the butter instead of letting it soften to room temperature? Time. The first time I made these, it was an impromptu decision. I microwaved for 45 seconds, which results in accidentally melting some of the butter, but it seemed to work fine.

Salted or unsalted butter? I don’t think it really matters. If you use unsalted butter, you could add a pinch of salt later on when adding the baking soda, but you don’t have to. I went rogue and used salted butter for this. Actually, I do that for most recipes, even when they call for unsalted. Why?

Cream together butter and brown sugar (1½ cups) on medium speed until mixture gets light and fluffy, about 2 minutes. Don’t skimp on this step!

Light brown sugar or dark brown sugar? I used light brown, but if you just have dark, go for it!

Reduce mixer speed to low. Add 2 eggs one at a time and mix until fully incorporated, about 1 minute. Mix in vanilla (1 teaspoon). Mix in baking soda (1¼ teaspoon). Gradually add flour (2½ cups), about a half cup at a time, and mix until all flour is incorporated.Mix in candy pieces.

Using a spoon or cookie scoop, form dough into balls and place onto cookie sheets lined with parchment paper.

What if I don’t have parchment paper? These cookies are prone to sticking because of the caramel in the candy bar pieces. Some cookie sheets have nonstick qualities already, but I haven’t tested this recipe on a nonstick sheet. If you don’t have parchment paper or a silicone baking mat and are unsure how “nonstick” your cookie sheet is, use a cooking spray like original Pam to grease the cookie sheet. (Thank you to reader Cathy for sharing your experience with copper baking sheets in the comments!)

Bake for about 10 minutes until cookies begin to get brown. Let cookies cool on cookie sheet for about 5 minutes before removing from the cookie sheet. I recommend transferring them to a wire rack for cooling if you have one.