Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.

In a large mixing bowl, beat together the softened unsalted butter, cookie butter, brown sugar, and granulated sugar until smooth and fluffy.

Mix in the egg and vanilla extract until fully combined.

In another bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.

Gently fold in chocolate chips or crushed Biscoff cookies if desired.

Using a cookie scoop or spoon, drop rounded tablespoons of dough onto the prepared baking sheets, ensuring enough space between them to spread.

Bake in the preheated oven for 10-12 minutes, or until the edges are golden and the centers are just set.

Let the cookies cool on the baking sheets for a few minutes before transferring them to wire racks to cool completely.