Prep: Preheat your oven to 350° F. Line two cupcake pans with paper liners, in preparation for 16-17 cupcakes.
Start the Batter: In a medium mixing bowl, whisk together the flour, sugars, baking powder, cinnamon, and salt. Add the softened butter and oil, and mix on low speed for about 30-60 seconds, just until the butter starts incorporating and you have a sandy mixture with some drier sandy bits, and some unevenly incorporated chunks of butter coated in flour.
1 and 1/2 cups + 1 tbsp cake flour, spooned & leveled or weighed out , 1 cup granulated sugar, 3 tbsp light brown sugar, packed, 1 and 1/2 tsp baking powder, 1/2 tsp cinnamon, 1/8 tsp salt, 7 tbsp salted butter, softened at room temperature , 2 tbsp vegetable oil
Finish the Batter: In a 2-cup glass measuring cup, whisk together the sour cream, milk, water, and vinegar until combined. Add 2 tbsp of this mixture to the bowl of butter and flour. Mix on low speed just until the mixture starts to come together (no more dry bits!), but is still lumpy. (See photos in blog post above for a visual). Then, add the vanilla and eggs to the remaining liquid mixture, lightly beating the eggs with a fork to break them up. Pour half this mixture into the bowl of batter with your mixer running on low. When it's almost incorporated, pour in the remaining liquid, mixing on low until just combined. Scrape the bowl to make sure everything is mixed in - a few small lumps is fine! Gently fold in the biscoff crumbs Do not over mix. 1/3 cup + 1 tbsp milk, at room temperature, 1/2 cup full-fat sour cream, at room temperature, 1 tbsp warm water, 1/2 tsp vinegar, 1 tbsp vanilla bean paste, 2 large eggs, at room temperature , 7 biscoff cookies, in fine crumbs
Bake: Divide the batter evenly among your 16-17 cupcake papers. Fill them about 2/3 full, or use 52 grams of batter per cupcake (I like precision!). Bake for 14 to 17 minutes. A toothpick inserted into the center should pull out moist crumbs, not wet batter. Immediately use a butter knife to pop the cupcakes out of the hot pan, and place them on a wire rack to cool completely. Fill the Cupcakes: Once cool, use a cupcake corer or a teaspoon to remove the center of the cupcakes, going about halfway down the cupcake. Fill each cupcake with 1-2 tsp of melted cookie butter (add it to a piping bag and snip the tip to make this part easy!).
3/4 cup cookie butter, melted
Make the Frosting: While the cupcakes cool, make the frosting. In a medium bowl, beat the butter until creamy, 30-60 seconds. Beat in the cookie butter. Add the powdered sugar and mix until combined, using a bit of water/milk as needed to help things along. Mix in the remaining frosting ingredients, adjusting to taste. If for some reason your frosting is too soft or weepy, pop the bowl in the fridge or freezer to stiffen it back up. Fill a piping bag fitted with a Wilton 1Mtip, then pipe swirls of frosting onto the cooled cupcakes. Drizzle with melted cookie butter and add half a biscoff cookie to each cupcake. Sprinkle with cookie crumbs. 1/2 cup + 2 tbsp salted butter, softened at room temperature , 1 cup cookie butter, 3 cups to 3 and 2/3 cups powdered sugar, 2-3 tbsp milk/water/heavy cream, 1 tbsp vanilla bean paste, pinch of salt, to taste, 1/8 tsp cinnamon, biscoff cookie halves, melted cookie butter, for drizzling
Serve + Store: Dig in immediately once the cupcakes are frosted! Store in an airtight container in the fridge for 2-3 days. Let cupcakes come back to room temperature on the counter before enjoying (or eat them cold, if you like a denser texture!)
Freezing Instructions: These cupcakes freeze well with or without frosting! Freeze in a freezer-safe container for 1-2 months. Let thaw on your counter for 1-2 hours before enjoying.