In a medium non-stick saucepan, combine milk, sugar, and cornstarch; whisk well and simmer on medium-low heat, whisking constantly until mixture has slightly thickened, about 10 to 15 minutes.

In a large bowl whisk egg yolks. Slowly add about 1 cup of the hot milk mixture through a mesh sieve to the yolks, whisking in about a tablespoon at a time to temper the egg so the egg doesn't cook.

Once the eggs are tempered, whisk in the remaining milk through the sieve then return to the sauce pan.

Melt the chocolate squares in the microwave 20 seconds at a time, up to a minute, stirring in between until the chocolate is melted. Pour melted chocolate into the sauce pan, whisk well.

Add vanilla; simmer on low for 15 minutes, whisking constantly.

Transfer the chocolate pudding into a large bowl, cover with wax paper, touching the pudding so that it doesn't allow a film to settle on top.

Refrigerate for at least 2 hours or overnight, it will further thicken in the refrigerator.

To make parfaits, when chilled, place 3 tablespoons of the pudding into each glass, then add 2 tablespoons of whipped topping in each, then 2 tablespoons more pudding and top with a dollop of Truwhip.