Meanwhile, line a baking sheet with a piece of parchment paper. Crush 16 Biscoff cookies into medium-coarse crumbs using a food processor or by placing them into a bag and crushing them with a rolling pin.
In a large bowl combine 2.5 cups of all purpose flour, 1 teaspoon of baking soda, 1.5 teaspoons of kosher salt, and 1.5 teaspoons of cinnamon. Add about half of the crushed Biscoff cookies (about 63g), reserve the rest for later. Mix well and set aside.
In a separate large bowl with a hand mixer or in a stand mixer with the paddle attachment, beat together the 12 tablespoons of softened butter, 1 cup of brown sugar, and ½ cup of granulated sugar. Beat until light and fluffy (about 4-5minutes), scraping down the bowl halfway.
Add in ¾ cup (180g) of cookie butter spread. Mix on medium speed until smooth and well incorporated.
Add in 1 tablespoon of vanilla extract and 1 egg. Mix until just combined, then add in 1 egg yolk. Mix until combined, and be sure to scrape down the bowl to ensure everything is incorporated.
Gently add the dry ingredients to the wet ingredients, mixing gently until a dough starts to come together. Switch to a rubber spatula about halfway through to avoid overmixing, and stop mixing as soon as no more dry streaks of flour remain.
Using a food scale, weigh out 16 portions of cookie dough that weigh 66-67g each and roll them into a round shape. This is about the size of a large cookie scoop.