Microwave the butter for about 40 seconds. Whisk until the butter is completely melted.
½ cup butter
Add the sugars, and mix until well-combined.
½ cup granulated sugar, ¼ cup light brown sugar
Stir in vanilla and egg until incorporated.
1 teaspoon vanilla extract, 1 large egg
Add the flour, baking soda, and salt. Please read the recipe note about properly measuring flour.
1 ⅔ cups all-purpose flour, ½ teaspoon baking soda, ¼ teaspoon salt
Mix dough until just combined. Dough should be soft and a little sticky but not overly sticky.
Stir in chocolate chips, mini marshmallows, and graham cracker crumbs.
½ cup mini semisweet chocolate chips, ½ cup mini marshmallows, ¼ cup graham cracker crumbs
Scoop out 3 tablespoons of dough (medium cookie scoop) and place 2 inches apart on baking sheet.
Bake for 10-15 minutes, or until cookies are set. They will be puffy and still look a little underbaked in the middle.
Notes
Butter: I use salted butter. If using unsalted butter, increase the salt to ½ teaspoon.
Measuring Flour: If you aren’t weighing your ingredients, I can’t recommend that enough. If you are using measuring cups, be sure to sift or stir the flour before measuring. Flour packs easily and using too much flour in cookies will give you dry, crumbly dough and cookies that don’t spread.
Marshmallows: You can use marshmallow bits; however, you won't have gooey marshmallows in the cookies with marshmallow bits.
Chocolate: I don't recommend using Hershey's bars in the cookies as it causes the cookies to spread more.