Step 1

Prepare cookie crust: Preheat oven to 300-degrees F. Spray 2 8-inch baking pans with cooking spray and line with parchment paper. Set aside.

Step 2

20 minutes
Combine all dry ingredients in a medium-sized bowl. Stir well. Add melted butter and mix until all the dry has been moistened. Divide crumb mixture evenly between both baking pans. Use the back of a spoon to press the crumbs into the base of the pans. Bake for 20 minutes. Remove from oven and set aside to cool.

Step 3

2 minutes
While cookie crust is baking, prepare cake layers: Beat butter until light and fluffy, 3 minutes or so. Add vegetable oil and sugar and beat another 2 minutes. Add eggs, yolk, and vanilla. Stir in baking powder and salt. Alternately add sour cream and flour in three batches, starting and ending with cake flour.

Step 4

25-30 minutes
Distribute batter evenly between both pans, over cookie crust. Bake 25-30 minutes (keeping oven temperature at 300-degrees F.) Cool cakes in pans for 10 minutes before inverting onto wire racks to cool completely.

Step 5

15-20 minutes.
While cakes are cooling, prepare brown sugar frosting: In a medium-sized saucepan combine brown sugar, corn syrup, and water over medium-heat. Bring the mixture to a soft boil and simmer 5 minutes, to thicken. Remove from heat and let cool 15-20 minutes.

Step 6

5 minutes.
Beat butter in the bowl of a stand mixer on medium-high speed for 3 minutes, until light and fluffy. With the mixer on low speed, add the powdered sugar in small batches. Once all the powdered sugar has been incorporated, stream the cooled brown sugar syrup into the bowl. Turn the mixer up to medium-high and beat for 5 minutes.

Step 7

10 minutes.
Assemble Pirouline cookie cake: Spread a small dollop of frosting on the cake plate, where the layers will be placed, just to adhere the cake to the plate. Place a cooled cookie crust-cake layer on top of the spread frosting. Spread a layer of frosting on top of cake layer. Top cake layer with a fine dusting of Pirouline cookie crumbs. Place second cake layer atop the frosting and Pirouline crumbs. Spread a crumb coat of frosting on top of, and around, the two cake layers. Place in freezer for just 10 minutes. Finish off cake with remaining frosting and garnish as desired with more Pirouline cookies and crumbs.