Preheat the oven at 325°F.
Place a deep baking dish larger than the cake pan in the oven. Half fill with water. This will be the water bath for the cake.
Add cream cheese to a cake mixer. Gently combine until smooth.
Mix in sugar and corn starch. Incorporate on a low speed.
Turn off the mixer and scrape the sides and base of the mixing bowl.
Pour in sour cream, vanilla, coffee powder, cocoa powder, and salt.
Mix by hand with a whisk or with the cake mixer on a low speed.
Add one egg at a time and incorporate fully before adding the next.
Scrape the sides and base of the mixing bowl again, making sure the filling is well mixed and uniform.
Pour the filling into the baking pan over the cooled cookie base.
Tap the pan on the counter several times to remove air pockets within the filling (it’s ok if they are there).
Place the pan in the water bath.
Bake for 1 hour.
After 1 hour, carefully shake the sides of the cake pan. If the filling has not set on the sides and is too jiggly, add 5 to 10 minutes to the bake time and recheck the cake. If the filling has set on the sides and the center jiggles slightly, turn off the heat.
Open the oven door slightly. Leave the cake to cool down in the oven for 1 hour.
Remove from the water bath. Set aside to cool down completely to room temperature.
Cover and place in the fridge to chill overnight.