Cream butter and sugars

• Beat the softened butter with the brown sugar and granulated sugar until smooth.

Add the wet ingredients

• Mix in the egg, egg yolk, vanilla extract and Biscoff spread until fully incorporated.

Fold in the dry ingredients

• Whisk together the flour, cornstarch, baking soda and salt.
• Fold the dry mixture into the wet mixture until just combined.

Add the mix-ins

• Fold in the chopped white chocolate and crushed Biscoff cookies.

Shape the dough balls

• Scoop heaping tablespoon portions of dough and place them on a lined baking sheet.

Bake

• Bake at 180 °C until the edges are set but the center is still soft.
• Let the cookies cool on the tray; if they look underbaked, return them to the oven briefly.

Decorate

• Drizzle the cookies with the reserved Biscoff spread and top with white chocolate and crushed Biscoff cookies.
• Neaten the edges with a large cup or cookie ring while still warm.