To make cookie cups: Preheat oven to 325 degrees. Spray a mini muffin tin liberally with non-stick spray.
Cream together the butter and Crisco. Add in sugars and eggs and mix once more. Add in 1/2 the flour, the baking soda, baking powder and salt. Mix well. Add in remaining flour and mix until combined. Stir in chocolate chips.
Scoop a rounded 1 1/2 TBSP (I use this cookie scoop here) into each mini muffin cup. Bake for 15 minutes. Let cool in pan for about 5 minutes, then press a teaspoon into each cookie to make a well.
Let cookies cool completely prior to taking them out of the tin. (To speed the process up, you can place them in the freezer for 5-10 minutes.)
Place a metal mixing bowl in the freezer while cookies are cooling. This helps to make the heavy cream whip faster.
Carefully remove each cookie cup from the tin.
To Make Mousse: In the metal mixing bowl, place the whipping cream and powdered sugar. Mix on medium-high for about 5 minutes, until cream holds stiff peaks. Spoon in Nutella and mix again just until Nutella is incorporated. Don't over mix! Scrape sides of the bowl and transfer mousse into a piping bag. Pipe mousse into each cookie cup. Place about 2 TBSP of Nutella in a sandwich bag and clip the corner. Drizzle additional Nutella on top of mousse cups.
Store in an airtight container in the fridge for up to 5 days.