Preheat the oven to 350. Line a cupcake tin with cupake liners
In a small bowl melt the butter and ¼ cup cookie butter together in the microwave for about 30 seconds.
In a large mixing bowl combine the flour, sugar, salt, and baking powder. Add the melted butter/cookie butter mixture, eggs, buttermilk, water, oil and vanilla extract. Whisk until smooth.
Divide the batter between the cupcake liners, filling them about ¾ of the way full. Bake for 18-20 minutes. Cool completely before filling and frosting.
Melt 1/2 cup of Biscoff spread in the microwave for 15-20 seconds. You will use this to fill the cupcakes as well as drizzle on top for decoration.
In order to fill the cupcakes you will need to remove some of the cake in the center. You can use a cupcake corer, a spoon, or one of my favorite ways – a piping tip. I take the wide end of the tip and press down about halfway into the cupcake and then twist and remove. Remove the cupcake from the piping tip and repeat on the remaining cupcakes. I don’t put that piece of cake back on the cupcakes so you can snack on them or save them and turn them into cake pops. Spoon the melted cookie butter into the center of each cupcake.
Biscoff Buttercream
To make the buttercream beat the butter on medium speed for about 3-4 minutes until light and fluffy. Add the cookie butter spread, heavy cream, vanilla and mix. Gradually add the powdered sugar until you've reached a spreadable or pipe-able consistency. 2 cups worked well for me. Add a pinch of salt, to taste.
To decorate the cupcakes I used a Wilton 2D tip and a disposable piping bag to swirl the frosting on top of the cupcakes. If you don't have a piping bag you can use a large ziploc bag and cut one corner off about 1" up. You can also use an angled spatula or table knife to spread the frosting on the cupcakes.
Using a spoon, drizzle the remaining melted Biscoff (whatever you have leftover from filling the cupcakes) on top to decorate. Sprinkle with crushed Biscoff cookies, if desired. You can store these cupcakes in an airtight container at room temperature for 2 days.