For the cookies:
1 cup unsalted butter, room temperature
3/4 cup dark brown sugar
1/2 cup sugar
2 eggs
1 teaspoon vanilla
1 tablespoon honey
1 3/4 cup all purpose flour
1 teaspoon baking soda
1/8 teaspoon cinnamon
1/2 teaspoon salt
1 1/2 cups quick cooking oats
For the marshmallow frosting:
2 egg whites
1/2 cup sugar
1/4 teaspoon cream of tartar
1/2 teaspoon vanilla
1. Preheat oven to 350 degrees. Cover baking sheets with parchment paper, set aside.
2. In the bowl of a stand mixer cream together the butter, brown sugar, and sugar until light and fluffy. Add eggs, honey and vanilla and beat until incorporated.
3. In a separate medium sized bowl whisk together flour, baking soda, cinnamon, and salt. Slowly add the flour mixture into the butter mixture and mix just until incorporated. Stir in oats until evenly distributed. Transfer dough to a large mixing bowl (this is so you can use stand mixer bowl for the frosting) and chill in refrigerator for 15 minutes.
4. Remove dough from refrigerator and drop by tablespoons onto baking sheet (or even a bit smaller for smaller cookies). Bake for 8 to 10 minutes just until the edges start to brown. Cookies will seem moist in the middle but they will set up. Cool on baking sheet until set and then transfer to a cooling rack to cool completely.
5. To make the frosting, in a double boiler, add egg whites, sugar and cream of tartar and heat over simmering water. Whisking frequently, heat until egg whites become very frothy and sugar is dissolved (approximately 160 degrees). Carefully add egg mixture to the bowl of a stand mixer fitted with the whisk attachment. Whisk on high speed for several minutes until egg mixture will hold stiff peaks and is light in texture. Carefully fold in vanilla until incorporated.
6. Add frosting to a cooled cookie and then top with another cookie. Store in an airtight container.