Mouthful (Chocolate-Nutella-Orange-Cheesecake) Cake
For the cheesecake layer:
(from Piece of Cake via RecipeGirl)
ingredients:
16 ounces of cream cheese, softened
2/3 cup granulated sugar
pinch of salt
2 eggs
1/3 cup sour cream
1/3 cup heavy cream
1 teaspoon vanilla extract
directions:
Preheat oven to 325 degrees F. 
Place a large roasting pan on the lower third rack of the oven. 
Place a kettle of water on the stove to boil. 
Spray a 9-inch springform pan with nonstick spray and line the bottom with a round of parchment paper. 
Wrap a double layer of foil around the bottom and up the sides of the pan (you want to seal it so the water from the water bath doesn’t seep into the pan). 
In a large bowl, use an electric mixer to mix the cream cheese- blend until it is nice and smooth and creamy. 
Mix in sugar and salt and blend for 2 minutes, scraping down sides of the bowl as needed. 
Add eggs, one at a time, blending after each addition. 
Finally, mix in sour cream, whipping cream and vanilla. 
Mix until smooth. 
Pour the batter into the prepared pan. 
Set the pan into the roasting pan in the pre-heated oven. 
Carefully pour the hot water from your kettle into the roasting pan (it will fill the pan surrounding the cheesecake). 
Pour enough water so that there is about an inch of water coming up the foil along the sides of the cheesecake pan. 
Bake the cheesecake for 45 minutes. 
It should be set to the touch and not jiggly. 
Remove the cheesecake from the roasting pan and let it cool on a wire rack for at least an hour. 
When it has cooled, place the pan into the freezer and let the cheesecake freeze completely. 

For the cake layers:
adapted from Gourmet via epicurious
ingredients:

2 1/2 cups flour
1/4 cup cornstarch (you can also use 2 3/4 cups cake flour, omitting the cornstarch and AP flour)
2 1/2 teaspoons baking powder
1/2 teaspoon salt
1 1/2 sticks unsalted butter
1 1/2 cups sugar
4 large whole eggs
zest of one entire orange
1 1/2 teaspoons vanilla
1/3 cup orange juice, freshly squeezed
1/3 cup sour cream or buttermilk
1/3 cup milk
handful of mini chocolate chips; enough for a healthy sprinkling on two 9 inch layers
directions:
Preheat oven to 350 degrees F.
Grease and flour two 9-inch cake pans.
Rub the sugar and zest together with your fingers until very fragrant.
Beat the butter until softened, then add in the orange sugar.
Cream together until very fluffy and light, about 3 minutes.
Beat in eggs one at a time, scraping after each addition, then add in the vanilla.
Stir the sour cream, juice, and milk together.
Stir the flour, cornstarch, baking powder, and salt together.
Either alternate adding the wet and dry or slowly dump them in at the same time (my preferred method… Just go slow so the flour doesn’t go all over).
Mix just until homogeneous, then pour into prepared pans.
Sprinkle the mini chocolate chips over the batter, and bake until golden and springy to the touch, about 20-25 minutes.  A cake tester should come out nearly clean, with perhaps just a few crumbs sticking on.
Allow to cool completely before assembling the cake.
For the frosting:
ingredients:
2 sticks butter
1 3/4- 2 cups confectioners’ sugar
big pinch salt
3/4 cup Ovaltine
1/2 cup nutella
splash vanilla extract
splash cream, if needed
directions:
Beat butter until soft, about 2 minutes.
Add in the ovaltine, nutella, salt, and vanilla, and beat to combine.
Slowly add in the powdered sugar, tasting to check the sweetness. (If you need more powdered sugar to thicken the consistency, be sure to add in a pinch more salt; you can also add in some more ovaltine for thickening.)
Play with the amount of powdered sugar to thicken the frosting; environments differ and really affect the thickness/pipeability.  If you need it to really thicken, don’t add too much more sugar or ovaltine, instead, stick it in the freezer for a few minutes to firm up.
If your frosting is too thick, add a splash of cream, about 2 teaspoons at a time, to thin it out a bit.  Don’t add too much, and wait between additions, because if it becomes soupy, there’s no going back.
To assemble:
Apply a thin layer of icing on the chocolate chip side of the first layer.
Place the frozen cheesecake layer on top, and spread another thin layer on top of that.
Place the second cake layer, chocolate chip side up, on top of the cheesecake.
Crumb-coat the whole cake in a thin layer of frosting, then chill it, either in the freezer or fridge, for 10-15 minutes in the freezer or 15-20 in the fridge.
Take the cake out and generously frost it with the remaining icing.
To smooth out the sides, dip an offset spatula in hot water, wipe it off, and gently run it on the outside of the cake.

Top with chocolate curls, if desired.