Preheat your oven to 350°F (175°C) and grease and line two 8-inch round cake pans with parchment paper.

In a medium bowl, sift together 1 and 3/4 cups all-purpose flour, 2 teaspoons baking powder, 1/2 teaspoon salt, and 1/2 teaspoon ground cinnamon.

In a large bowl, beat 1/2 cup softened unsalted butter and 3/4 cup granulated sugar on medium speed for 3 to 4 minutes until pale and fluffy.

Add 2 large room-temperature eggs one at a time, beating for 30 seconds after each addition.

Beat in 1/2 cup Biscoff spread for 1 to 2 minutes until fully incorporated.

With the mixer on low, alternate adding the dry ingredients and 1/2 cup whole milk in three additions, beginning and ending with dry ingredients, mixing until just combined.

Stir in 1 teaspoon vanilla extract, then divide the batter evenly between the prepared pans.

Bake for 32 to 38 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.

Let the cakes cool in the pans for 10 minutes, then transfer to a wire cooling rack and cool completely, about 1 hour.

To make the frosting, beat 1/2 cup softened unsalted butter and 3/4 cup Biscoff spread on medium speed for 2 minutes, then add 1 and 1/2 cups powdered sugar and 1/4 teaspoon salt on low speed until combined. Add 1 tablespoon heavy cream and beat on medium for 1 minute until fluffy.

In a small bowl, combine 12 crushed Biscoff cookies, 2 tablespoons melted unsalted butter, 1 tablespoon brown sugar, and a pinch of sea salt to form the crumble topping.

Level the cooled cake layers with a serrated knife or cake leveler.

Place one layer on a serving plate, spread a thin layer of frosting on top, add the second layer, and frost the top and sides of the cake.

Chill the frosted cake for 15 minutes to set the frosting.

Press the crumble topping onto the top and sides of the cake until evenly covered.