Line an 8x8 square pan with baking paper.
Heat the heavy cream over low heat in a saucepan and add the sweetener, butter and vanilla extract. Stir to dissolve.
Let it cool down for a couple of minutes and add the chocolate chips to the mixture. Stir to melt into a smooth, velvety consistency.
Pour into the prepared pan and freeze for at least 20 minutes.
In the meantime make the frosting: With an electric blender beat the cream cheese, Erythritol, heavy cream, and mint extract to get a smooth frosting.
Fold in the food coloring if using any.
Spread the mint frosting over the frozen chocolate layer evenly. Cut into squares and top each one with the dried cranberries, if using any.
Serve cold.