Toast the nuts, if using. If you choose to add nuts, start by toasting them for 5 - 8 minutes at 350 degrees. Then set them aside to cool.
Bring a small saucepan of water to a boil. In a large heatproof bowl, combine the heavy cream, sweetener, butter, and chocolate chips.
Then, place the bowl over the pot of boiling water - being sure the bottom of the bowl doesn't touch the water. Stir until everything is melted and creamy.
Remove from heat and stir in some vanilla, a pinch of salt, and nuts (if using). Pour into a greased and foil-lined pan. Place in freezer for 1 hour to set up.