Optional Biscoff cake crumb (for texture between layers and decorating outer base of cake)

1. Start making your crumb by preheating the oven temperature to 300°F and lining a quarter sheet pan or baking sheet with parchment paper.
2. In a bowl or bowl of your stand mixer, combine all the dry ingredients for the crumb (sugars, flour, baking powder, crumbled Biscoff cookies, salt, and spices). Add to stand mixer bowl if not already using. Combine oil and vanilla in a small container and stream the liquid into the mixer while paddling on low.
3. Mix until you see small clusters of your ingredients forming, and use your hands to clump the mixture together and spread out on your baking sheet.
4. Bake crumb for about 20 minutes, or until light golden brown. Let cool completely.

Biscoff cake layers

1. Increase the oven’s heat to 350°F. Butter and flour two 6” round cake pans or coat them with baking spray before proceeding. If using cake strips (highly recommend), secure damp ones around both of your cake pans.
2. To a large mixing bowl, add and whisk together all-purpose flour, baking powder, baking soda, kosher salt, and ground cinnamon. Set aside.  
3. Using the paddle attachment in the bowl of a stand mixer, cream your unsalted room temperature butter, vanilla extract, and sugars together on medium speed for 3 minutes. Stop mixer and scrape down the sides of the bowl. Add the eggs one at a time, mixing between each one, before mixing batter all together on medium speed for 1 minute.
4. Add half of your bowl of dry ingredients and all buttermilk to your mixing bowl and mix on low for about 45 seconds.  
5. Add remaining flour, along with your Greek yogurt, oil, and Biscoff spread. Mix on low speed until totally incorporated.  
6. Pour and evenly spread the batter into your prepared cake pans (about 350 grams in each pan). Bake for 45 - 50 minutes, at which point you can insert a toothpick to test if your cake's done by inserting it into the layers and seeing if the toothpick comes out cleanly.
7. Let cake cool in pan about 10 minutes before transferring to a wire rack to cool completely.

Biscoff Buttercream 

1. In the bowl of your stand mixer, combine your unsalted butter, powdered sugar, vanilla extract, heavy cream, salt, crumbled Lotus cookies and Biscoff spread. Start mixer on a low setting to avoid powdered sugar from flying everywhere. Then increase speed and beat for another 3-4 minutes.  
2. Fit a piping bag with a large round tip over the rim of a glass to scoop and transfer frosting into it.

Biscoff Cake Assembly

1. Pipe a dollop of buttercream onto a cake circle to act as glue to hold the layer in place. Set first cake layer on top of that.
2. Pipe roughly ⅓ of your Biscoff buttercream on top of the bottom layer and sprinkle about ½ of your cake crumb. Use your hands to gently press the crumb into the frosting so it sticks to it. Add another coat of frosting on top to hold the crumb in place.
3. Place second cake layer on top of the first. Then, starting from the base of the cake and moving to the top, pipe a thick layer of frosting around your cake.
4. If you want the marbled effect, place 2-3 spoonfuls of Biscoff spread in a microwavable container for about 15 seconds on medium power. You want the texture to be warm and easily spreadable.
5. Use a spoon to swipe small dollops of the melted spread around your cake. Then place a cake scraper against the side of the cake and gently pull the cake around to smooth out the frosting and create a marble design.
6. Fill in any gaps in the frosting with your Biscoff buttercream, but refrain from marbling and smoothing the cake more than 3 times. The spread will start to harden, making it messier and more difficult to smooth the cake’s sides.
7. Add any remaining melted buttercream to the cake top and spread it with a spoon or offset spatula.
8. Gently press remaining crumbs all around the base of your cake and on top for extra crunch and Biscoff flavor!