Grease and flour two 9-inch cake pans, lay parchment paper on the bottom and grease again.
In a large bowl, or in the bowl of an electric mixer, combine flour, salt, baking powder, baking soda, cocoa and sugar.
Add canola oil, followed by the hot coffee and mix on low-medium speed. Add eggs, heavy whipping cream, and vanilla, and mix until combined.
Using a spatula stir in the chocolate chips.
Pour the batter evenly into both 9-inch cake pans and bake for 25 to 35 minutes, until a wooden tooth pick inserted into the center of the cake comes out clean. Switched the pans around 12-15 minutes of baking, from the middle shelf to the bottom and the bottom shelf pan to the top, to ensure even baking.
Remove cakes from oven and let cool completely before removing from pans. Once cooled, transfer to a wire rack.
The cakes should cool completely on the wire rack before frosting.
Oreo Buttercream:
In the bowl of an electric mixer, fitted with the wire attachment, beat together butter until smooth.
Slowly add 4 cups of powdered sugar and mix until smooth. Pause to scrape the sides of the bowl. Add vanilla extract, Oreo crumbs and remaining sugar, mix until smooth.
Add milk until you get a smooth, desired consistency.
Use immediately or cover and refrigerate up to three days. To use once refrigerated, slowly allow reaching room temperature and then beat on low speed until the buttercream is smooth before using.
Nutella Buttercream:
Cream together butter and 1 ½ cup of confectioner’s sugar, once combined add Nutella and whisk until combined. Add vanilla, pinch of salt and the rest of sugar, mix until smooth, pausing to scrape the sides of the bowl. Beat on high for about 20 seconds to lighten the frosting.
Add heavy cream, one tablespoon at a time until the buttercream has reached a consistency where it holds its shape. Whip on high for a final 20 seconds.
Use immediately or cover and refrigerate up to three days. To use once refrigerated, slowly allow reaching room temperature and then beat on low speed until the buttercream is smooth before using.
Assemble the cake:
Place first layer of cake on a cake plate and cover with a very thick layer of Oreo buttercream.
Add second layer of cake and cover it with a thick layer of Nutella buttercream, ice the outside of the cake with a combination of Nutella and Oreo Buttercream.
Finish cake off with chopped roasted hazelnuts, mini Oreos and Oreo crumbs.