Preheat your oven to 350°F (177°C) with convection and line 13 muffin tins with cupcake liners.

In a medium bowl, whisk together the cake flour, baking powder, salt, and sugar until evenly distributed.

Add the canola oil and salted butter to the dry mixture and beat until well combined. Then incorporate the egg, vanilla extract, and vanilla bean paste, mixing until fully blended.

Stir in the sour cream and, while on low speed, stream in the whole milk. Scrape the sides and mix just until smooth.

Place half of a Biscoff cookie at the bottom of each liner, fill each liner halfway with the batter (about 30-32 grams), add a teaspoon of cookie butter in the center, and cover with enough batter until each liner is 3/4 full.

Bake in the preheated oven for 20-21 minutes, or until golden and spring back when pressed.

Remove from the oven and let the cupcakes cool in the pan for 10 minutes before transferring to a cooling rack to cool completely.

In a saucepan, combine sugar and water, swirl until sugar is fully immersed and heat over medium until dissolves.

While the sugar syrup cooks, whip eggs in a stand mixer until frothy.

Monitor the syrup until it reaches 240°F (116°C). Then slowly drizzle it into the whipped eggs while continuing to whisk.

Whip the mixture on high for 5-10 minutes until pale, fluffy, and cool to touch.

Add softened unsalted butter 2 tablespoons at a time, mixing until incorporated.

Add vanilla, cookie butter, and salt, whip on high for another 1-2 minutes. Refrigerate if too soft.

Frost the cooled cupcakes using a piping bag fitted with a large round tip.

Microwave cookie butter for about 10 seconds until runny and drizzle over the frosted cupcakes, then sprinkle with crumbled Biscoff cookies.