Add the chocolate and butter together and melt them over low heat. Or use microwave to melt butter and chocolate.
When the chocolate mixture is completely melted, remove from the heat and whisk with the vanilla, erythritol and peppermint. Add some salt if necessary.
In a bowl, whip the heavy cream and add chocolate mixture.
Mix the ingredients thoroughly until homogeneous.
Gently spread the mix on a non-stick pan or any other pan covered with parchment paper or plastic wrap. Leave in the freezer for 3-4 hours.
Slice the chilled chocolate fudge into bite-sized cubes. The amount may depend on the size of the pan and the cubes themselves.