Equipment Needed
- Two large baking sheets
- Parchment paper or silicone baking mats (a lifesaver for cleanup)
- Electric hand mixer or stand mixer
- Large mixing bowls
- Measuring cups and spoons
- A sifter or fine-mesh strainer for the dry ingredients
- A sturdy spoon or a cookie scoop (I use a #40 scoop for perfect rounds)
Step-by-Step Instructions
First, we’ll get our cookies ready. I always start by preheating my oven to 375°F (190°C) and lining my baking sheets with parchment paper. In a medium bowl, I whisk together the flour, that gorgeous dark cocoa powder, baking soda, and salt. Getting out any lumps here is key for a tender crumb. In my larger mixing bowl, I cream the softened butter and sugar together with my hand mixer until it’s light and fluffy—this takes about 3 full minutes, so don’t rush it. Then I beat in the egg and vanilla until everything is beautifully combined.
Now, here’s the part where I learned a valuable lesson about patience. With the mixer on low, I add the dry ingredients and the buttermilk in three alternating additions, starting and ending with the dry ingredients. The batter will look a little shaggy at first, but just keep mixing on low until it just comes together. Overmixing is the enemy of a soft cookie! Using my cookie scoop, I drop rounded tablespoons of batter onto the prepared sheets, leaving about 2 inches between them because they do spread.
Into the oven they go for 10-12 minutes. The trick is to pull them out when the tops look set and spring back lightly when touched. Don’t wait for cracks to form; they’ll continue to cook on the sheet for a minute. I let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Trying to fill a warm cookie is a recipe for a melty, messy disaster, as I discovered the hard way my first try!
While the cookies cool, I make the filling. This is the fun part. I beat the softened butter for a good 2 minutes until it’s pale and creamy. Then, I gradually add the sifted powdered sugar on low speed, unless I want a blizzard in my kitchen. Once incorporated, I beat in the marshmallow fluff, vanilla, and that all-important pinch of salt. I then crank the mixer to medium-high and beat for a full 3-4 minutes. I promise, this waiting game is crucial—it transforms the filling from grainy and dense to impossibly light, fluffy, and cloud-like.(See the next page below to continue…)