I had these cookies for the first time at a Halloween party a long time ago, and therefore I always associate them with Halloween. I don't know for sure exactly what elements are required for a true monster cookie, but these are at least a close relative of monster cookies. While there's no small amount of sugar in these, they somehow don't taste overly sweet, which I appreciate.

1 cup (8 oz.) butter, softened
1 cup (9.5 oz.) natural peanut butter
1 1/2 cups (12 oz.) brown sugar
1 cup (7 oz.) granulated sugar
2 eggs, room temperature
2 teaspoons vanilla
2 cups (7 oz.) old-fashioned oats*
1 1/2 cups (7 7/8 oz.) whole wheat flour
1 teaspoon baking soda
12 oz. chocolate chips**
2 cups M&M's
1 cup chopped walnuts (optional; I didn't use them)

Preheat oven to 325°F. Line two baking sheets with parchment paper.

Using a stand mixer (or sturdy electric hand mixer and a large bowl), cream butter and sugars for approximately 3 minutes, until light and fluffy. Scrape down sides of bowl.

Add eggs and vanilla, mixing for about 1 minute.

Add oats, flour, and baking soda. Mix until combined, about 30 seconds. Stir in chocolate chips, M&M's, and walnuts (if using).

Use a cookie scoop, spoon, or your hands to form dough into 1.5-inch balls. Place about 2 inches apart on cookie sheets.

Bake for 10-15 minutes, rotating sheets on top and bottom racks halfway through. When done, the tops of the cookies should be just beginning to brown. Remove cookies from the oven and transfer to a wire rack to cool completely.

Store in an airtight plastic container or ziplock bag for up to 1 week.

*The recipe calls for quick-cooking oats, but I didn't have any, and I thought the cookies turned out great with old-fashioned oats.
**I used Ghirardelli bittersweet chips because I love them, but any variety will do.

Recipe source: a lovely woman named Amy who may or may not have originally gotten the recipe from a Martha Stewart magazine