Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper or silicone baking mats. In a food processor, pulse 16 of the Biscoff cookies until they form about 1 cup of fine crumbs; set these crumbs aside. Roughly break another 8 cookies into chunks and set those aside as well. Reserve the remaining 8 whole Biscoff cookies for decorating the tops of the cookies after baking.

In a large bowl, cream together 1 cup cold salted butter, 1 cup packed light brown sugar, and ½ cup granulated sugar for 3 to 4 minutes until fluffy. Add 2 large eggs and 2 teaspoons vanilla extract, then beat again, pausing to scrape down the sides and bottom of the bowl to ensure even mixing. Stir in 1 cup of Biscoff cookie butter until fully incorporated.

Next, add 2¾ cups all-purpose flour, the reserved 1 cup of finely crushed Biscoff cookie crumbs, 2 teaspoons cornstarch, 1 teaspoon baking soda, ½ teaspoon baking powder, and ½ teaspoon salt. Mix on medium-low speed just until everything is combined, stopping occasionally to scrape down the bowl. Fold in the reserved cookie chunks along with 1½ cups white chocolate chips.

Using a large ¼-cup cookie scoop, portion out the dough into evenly sized balls. If you want perfectly uniform cookies, gently roll each dough ball between your hands. Arrange the dough balls on the prepared baking sheets, spacing them a few inches apart to allow room for spreading during baking. (See notes if you plan to stuff the cookies with extra cookie butter.)

Bake the cookies for 8 to 10 minutes, just until they are set around the edges but still slightly soft in the center, so they remain chewy. Remove the baking sheets from the oven and immediately press half of one of the reserved whole Biscoff cookies onto the top of each cookie, along with a few extra white chocolate chips. Let the cookies cool on the baking sheets for 10 minutes before transferring them to a wire rack to cool completely.