Brownie Cake: Preheat oven to 350 degrees. Spray a 9-inch springform pan with nonstick cooking spray.

Melt butter in a medium saucepan over medium heat. Remove from the heat and add the chopped bittersweet chocolate. Let stand for 30 seconds, then whisk together until smooth. Add the brown sugar, vanilla and espresso powder and whisk until smooth. Whisk in eggs one at a time. Using a rubber spatula, fold in flour, baking powder and salt until the flour is no longer visible.

Spread mixture into the prepared pan and bake for 20-25 minutes until the cake has puffed slightly and is just barely cracked. Transfer to a wire rack to cool before removing from pan.

Speculoos Frosting: In a large bowl using a hand mixer at medium speed, mix together butter and speculoos until light and fluffy. Add the confectioner's sugar, salt and heavy cream. Beat for an additional minute.

Spread frosting on cooled cake. Garnish with chocolate shavings. Cut into wedges and enjoy!