Preheat oven to 350 degrees. Grease and line a 9" springform pan with parchment paper, set aside.
In a large bowl, cream butter and brown sugar together until light and fluffy. Beat in egg, egg yolk, vanilla and molasses until completely smooth. Add spices, baking soda and flour and mix until just combined. Dough will be sticky.
Press dough down into prepared pan. Using a rubber spatula or piece of foil sprayed with cooking spray will keep the dough from sticking so it's much easier to spread.
Bake for 22-25 minutes or until the top does't look "wet" anymore. Cookie cake will seem underdone when you take it out, but that is what keeps it so soft and chewy when it sets. If you'd like it to be crispier, bake for 2-3 more minutes. Once done, place pan on wire rack and remove the outer ring. Allow it to cool completely before frosting. At this time, if the cookie cake seems slightly "puffy" around the edges, flatten it very gently with the palm of your hand. Be careful it doesn't stick to your hand though!
While cookie cake is cooling, prepare frosting. Cream together the cream cheese and butter until completely smooth with no lumps. Add in the vanilla. Incorporate the confectioner's sugar one cup at a time until light and fluffy. Once the cookie cake is completely cool, you're ready to frost. If you want it the way I have it, scoop out 2-4 tbs of frosting and microwave for 10 seconds at a time until pourable. Drizzle over the cake. Next, dump icing into a piping bag and pipe around the edges and garnish with sprinkles. Alternatively, you can just frost the entire thing.
Gingerbread Cookie Cake will stay soft and fresh for up to 7 days stored in an airtight container.