Preheat your oven to 160ºC (320ºF) and line a 12-cup cupcake pan with liners.

Whisk together granulated sugar, dark brown sugar, all-purpose flour, baking powder, baking soda, and salt in a large mixing bowl.

In a separate bowl, mix the wet ingredients: sour cream, Biscoff spread, whole milk, vegetable oil, large eggs, and vanilla extract.

Carefully pour the wet mixture into the dry ingredients and gently fold them together until just combined.

Evenly divide the cupcake batter among the prepared cupcake liners, filling each about two-thirds full.

Bake for 20-23 minutes or until a toothpick inserted in the center comes out clean.

Cool in the pan for 5 minutes before transferring to a wire rack to cool completely.

Beat the softened butter in a mixing bowl until light and fluffy.

Gradually add the Biscoff spread and mix until well combined.

Slowly incorporate the sifted powdered sugar and milk, beating until the frosting reaches a smooth consistency.

Once the cupcakes are cool, pipe the buttercream frosting onto each cupcake.

Drizzle with warm Biscoff spread if desired.

Crumble Biscoff cookies on top of the frosted cupcakes.