Preheat the oven to 350°F (180°C) and line a cupcake tray with cupcake liners.
Sift all purpose flour into a mixing bowl and add light brown sugar, baking soda and salt. Mix together.
Prepare your homemade buttermilk (if you're using a homemade version) by adding 1 tablespoon of lemon juice to a measuring jug and then adding room temperature milk up to the ¾ cup (180ml) line. Let it sit for a minute to thicken and curdle.
Add buttermilk, melted biscoff spread, canola oil, egg and vanilla and mix into a batter. Don't overmix.
Divide the batter between the 12 cupcake liners.
Bake for 20 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean.
Let the cupcakes cool for a few minutes before transferring them to a wire cooling rack to cool completely before frosting.
Frosting. Add softened butter and biscoff cookie butter to the bowl of your stand mixer and beat together until smooth and creamy.
Add powdered sugar and milk and beat again for a few minutes until fluffy.
When the cupcakes are completely cooled, pipe on the frosting and then top with crushed biscoff cookies and decorate with a half biscoff cookie pressed into the top of each cupcake.