Preheat oven to 350°F and line a 8x8 or 9x9 square baking pan with parchment paper so the ends hang over the sides of pan and set aside
In a bowl whisk together flour, salt and baking soda and set aside
With your mixer cream together butter and both sugars on med-high until light and fluffy about 5 mins.
Add in egg and vanilla and mix
Combine your dry ingredients to your wet on low speed and mix just until combined.
Gently fold in your chocolate chips and Biscoff pieces
Press into prepared pan and then add dollops of Biscoff spread over top of dough and make swirls with a knife
Bake for 20-25 mins until edges golden brown in colour but still a little jiggle in middle it will continue to bake while cooling so you don't want to over bake it.
Remove from oven and let cool in pan for 15 mins before removing from pan and transferring onto a cooling rack to cool for another 25 mins before cutting into.