In a medium saucepan, combine the 3 cups of fat-free milk with 2 1/2 tablespoons of monk fruit sugar substitute, 1 1/2 teaspoons of vanilla extract, and 2 tablespoons of cornstarch. Whisk well until all ingredients are fully incorporated and there are no lumps.
Place the saucepan over medium heat and continue to whisk the mixture as it heats. It will begin to thicken as it approaches a gentle simmer.
Once the mixture is simmering, take a small bowl and beat the 2 large egg yolks. Gradually add a few tablespoons of the hot milk mixture to the yolks, whisking constantly to temper them.
Pour the tempered yolk mixture back into the saucepan with the rest of the milk. Stir continuously for an additional 2-3 minutes until the mixture thickens to a pudding-like consistency.
Remove the saucepan from the heat and add the 4 ounces of semi-sweet baking chocolate. Stir until the chocolate is completely melted and the mixture is smooth.
Transfer the chocolate mixture to a mixing bowl and allow it to cool at room temperature for about 30 minutes. Once cooled, you can refrigerate it for quicker cooling if desired.
In your serving glasses or jars, add a layer of the chocolate mixture, followed by a generous dollop of the 1 1/4 cups of Tru Whip whipped topping. Repeat the layers until the glasses are filled, finishing with a layer of whipped topping on top.
Cover the parfaits with plastic wrap and refrigerate for at least 2 hours to let the flavors meld and the parfaits set.
