Scoop 16 heaping teaspoons of cookie butter on a baking sheet or plate lined with parchment paper. Place in the freezer for 1 hour, or until the cookie butter is frozen. When it's ready, leave in the freezer while you make the cookie dough.
Preheat oven to 325°F and line 2 baking sheets with parchment paper.
In the bowl of a standing mixer with the paddle attachment or a handheld mixer, combine butter and sugars, mixing until light and fluffy. Add in the eggs and vanilla extract, and beat until just combined (do not over-mix!).
Mix in the cocoa powder, flour, baking soda, and salt until a dough forms. Don't over-mix!
Scoop 2 Tablespoon sized balls of dough and place them on the baking sheet. Make a small teaspoon-sized indent in each one.
Remove the cookie butter from the freezer and place one ball into each of the indented cookie dough balls. The cookie butter will start to soften right away so try to move quickly! If possible, assemble 5-6 cookies at a time, placing the plate of cookie butter back into the freezer in between.
Seal the biscoff balls but wrapping the cookie dough around them and roll the dough into a ball. Bake for 8-11 minutes, or until the edges and tops look set. Don't over-bake or else the cookies will not stay soft.
Let the cookies cool on the baking sheet for 10 minutes before transferring them to a wire rack to cool completely.