Preheat the oven to 350℉ (177℃). Line a cupcake pan with 12 cupcake liners.

In a medium mixing bowl, whisk together the all-purpose flour, baking powder, salt, and cinnamon. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl with an electric hand mixer, cream the granulated sugar, unsalted butter, and vegetable oil until light and creamy. Add the egg, sour cream, and vanilla extract and mix until well combined.

Add half of the flour mixture and mix on low speed. Pour in the milk while mixing on low speed and mix until combined. Add the remaining flour mixture and the Biscoff cookie crumbs and mix until all the ingredients are combined and smooth.

Portion the cupcake batter into the cupcake liners using a large cookie scoop (about ¾ full). Bake the cupcakes for 20 minutes until the tops of the cupcakes bounce back when gently touched. Cool the cupcakes in the pan for a few minutes and then transfer to a wire rack to cool completely.

In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl with an electric hand mixer, whip the room temperature unsalted butter for 5 minutes until light, pale, and creamy. Add the Biscoff spread and mix until combined and smooth.

Add in the powdered sugar and mix on low speed until fully combined. Add the vanilla extract and salt and mix well. While mixing on low speed, drizzle in the heavy cream. Scrape the sides and bottom of the bowl to ensure the ingredients are well incorporated.

Increase the mixer speed to medium and whip the buttercream for about 2 to 3 minutes until it is smooth and creamy. To smooth out the buttercream, mix the frosting on low speed for several minutes.

Use an apple corer to remove the center of the cupcakes. Melt the Biscoff spread in the microwave for 30 seconds. Fill a piping bag with the tip cut off with about ½ cup of the melted cookie butter. Pipe the melted cookie butter into the center of the cupcakes.

Fill a piping bag fitted with a Wilton 1M piping tip with the Biscoff buttercream frosting. Pipe a generous swirl of frosting onto the cupcakes. Drizzle the cupcakes with the remaining ¼ cup of melted Biscoff spread and decorate with Biscoff cookie crumbs and Biscoff cookies.