Step 1

In a small bowl, mix the peanut butter and confectioners’ sugar together until combined and smooth. You can just use a spoon for this. Mixture is thick, yet soft. With a teaspoon, scoop out a spoonful of peanut butter mixture (about 6g), and roll into a ball. Place on a parchment paper-lined baking sheet, plate, or tray. Repeat with remaining mixture until you have 24 peanut butter balls. Loosely cover and freeze for at least 1 hour and up to 1 day. (I usually just freeze them for a little over 1 hour, which is the amount of time it takes to make and chill the brownie cookie dough.)

Step 2

Melt the chocolate in a double boiler or use the microwave. Microwave in 20-second increments, stirring after each until completely melted. Set aside to slightly cool.

Step 3

Meanwhile, whisk the flour, cocoa powder, espresso powder, baking powder, and salt together. Set aside. In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter, brown sugar, and granulated sugar together on medium-high speed until smooth and creamy, about 2 minutes. Add the eggs and vanilla extract, and beat on high speed for 2 full minutes. Scrape down the sides and up the bottom of the bowl, then beat on high for 1 more minute. Pour in the slightly cooled melted chocolate and mix on medium-high speed for 2 full minutes. Pour the dry ingredients into the wet ingredients and beat on low speed until combined.

Step 4

Cover and chill the dough in the refrigerator for 1 hour. If chilling for longer, allow the cookie dough to sit at room temperature for 10-15 minutes before rolling and shaping in step 6.

Step 5

After chilling, preheat oven to 350°F (177°C). Line large baking sheets with parchment paper or silicone baking mats.

Step 6

The peanut butter filling softens up extremely quickly after you take it out of the freezer. I recommend taking about 6 peanut butter balls out of the freezer at a time, leaving the rest in the freezer while you’re shaping the first bunch. Using a sturdy tablespoon, scoop out a heaping spoonful of the cookie dough and roll into a ball, about 1.5 Tablespoons/30g/1 ounce of dough each. The dough will be quite stiff. Make an indentation with your thumb, and place a frozen peanut butter ball in the indentation. Pinch off a piece of the brownie cookie dough and press it on top of the peanut butter filling, and then roll the whole thing together into a smooth ball. Feel free to pull off pieces of brownie dough to expose more peanut butter and then re-roll together; peanut butter can also be hidden inside the cookie dough if you don’t want a marbled look. Repeat with remaining cookie dough and peanut butter balls. (Warning: your hands get messy in this step!)

Step 7

Place dough balls 3 inches apart on the baking sheets and bake for 12-13 minutes or until the edges appear set. The centers will be quite soft, but will set up as the cookies cool.

Step 8

Remove from the oven and allow cookies to cool on the baking sheet for 10 minutes before transferring to a wire rack to cool completely.

Step 9

Cookies stay fresh covered at room temperature for up to 1 week.