Line an 9x9 square baking pan with parchment or waxed paper.
In a medium saucepan over medium heat, whisk together cream and powdered sweetener. Bring to just a boil, then remove from heat. Stir in vanilla extract.
Add chopped chocolate and let sit 5 minutes until chocolate is completely melted, then whisk until smooth.
Pour half into the prepared pan and spread evenly to the edges. Transfer to the fridge for about 20 minutes to firm up, and put a lid over the remaining chocolate to keep warm.
For the mint layer, beat cream cheese, sweetener, cream, mint extract and green food coloring together until smooth.
Spread over first chocolate layer evenly, smoothing to the edges.
Top with remaining chocolate (you can rewarm gently, if needed), spreading evenly to the edges. Refrigerate until set, about 1 hour.