Scoop twenty half tablespoon sized balls of Biscoff cookie butter onto a parchment lined baking sheet. Freeze for at least twenty minutes so the centers stay gooey and do not leak while baking.
Add the butter to a saucepan and melt over medium heat. Stir constantly. It will foam and sizzle, then turn golden brown with toasted bits at the bottom. Once it smells nutty, remove from the heat and pour into a heatproof bowl. Cool for five to ten minutes.
Mix the cooled brown butter with the Biscoff cookie butter, brown sugar, and granulated sugar until smooth.
Add the eggs and vanilla and mix until glossy and fully combined.
Whisk together the flour, baking powder, cornstarch, and salt in a separate bowl.
Add the dry ingredients to the wet ingredients and mix on low just until combined. Do not overmix.
Fold in the white chocolate chips, crushed Biscoff cookies, and cookie crumbs until evenly distributed.
Chill the dough for thirty minutes.
Preheat the oven to 350 degrees F and line baking sheets with parchment paper.
Scoop two to three tablespoons of dough and flatten it in your hand. Place a frozen cookie butter ball in the center. Wrap the dough fully around it and roll into a smooth ball. Repeat with the rest of the dough.
Arrange the dough balls on the baking sheet, leaving two inches between each cookie. Bake for ten to twelve minutes until the edges are golden and the centers look slightly underbaked.
Top with half of a biscoff cookie if desired.
Cool the cookies on the baking sheet for ten minutes, then move them to a cooling rack. Enjoy warm and gooey.