Preheat oven to 350 degrees F.
In a mixer, mix together butter, Nutella, sugars, eggs and vanilla until smooth.
Add in flour, salt and baking soda until batter forms.
Stir in 3/4 C of chocolate chips and 1/4 C of toffee pieces.
Spray 10 " cast iron pan with non-stick spray.
Spoon in batter and press into pan leaving a 1/2" space around the skillet. This will allow the brownie to spread and the sides won't overcook.
Top with remaining chocolate chips and toffee pieces.
Bake for 25-30 minutes or until edges are set and tooth comes out clean.
Let cool on a wire rack until just warm.
It will be soft and gooey in the middle but as it cools it will set up.
Serve with ice cream