Preheat oven to 325°F degrees. Spray a mini muffin tin liberally with non-stick spray.
Cream together the butter and shortening. 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.) Carefully remove each cookie cup from the tin.
How to Make Nutella Mousse
Place a metal mixing bowl in the freezer while cookies are cooling. This helps to make the heavy cream whip faster.
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.
Notes
Store in an airtight container in the fridge for up to 5 days.