• Pre-heat the oven to 350℉ and line 2 cupcake pans with paper liners or spray with non stick spray. Set aside.
• In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
• In a separate bowl, whisk together the biscoff, brown sugar, sour cream, milk, oil, egg, and vanilla until well combined and no lumps of biscoff are left.
• Make a well in the dry ingredients and pour the wet ingredients into the dry. Mix together until combined.
• Scoop the batter into the muffin liners, filling about ¾ of the way full.
• Bake the cupcakes for 20-23 minutes, or until a toothpick comes out clean. Allow them to cool in the pan for 5-10 minutes, and then remove them to cool completely on a wire cooling rack.

Make the biscoff buttercream

• Combine butter and biscoff in a large bowl and use a stand mixer with a paddle attachment or a hand mixer to beat until creamy and well-combined.   
• With the mixer on low speed, gradually add the powdered sugar until completely combined, scraping the sides of the bowl as needed.
• Stir in vanilla extract and salt. With the mixer on low speed, add 1 tablespoon of milk and mix until combined. Add 1-2 more tablespoon of milk as needed. Gradually increase speed to high and beat for another 30 seconds to 1 minute.
• Pipe or spread the frosting onto completely cooled cupcakes.