Chocolate Truffle ice cream

I have very very little counter space, and subsequently very few kitchen appliances, but the ice cream maker has definitely earned its place in my kitchen and in my heart. I bought it because, well, most of you know how I am about ice cream, but I wanted to make it with less fat and different more interesting flavors. So, I give you my low-fat recipe for the most chocolatey delicious chocolate ice cream I've ever had. It actually tastes like a creamy frozen truffle. Modified from The Ultimate Ice Cream Book by Bruce Weinstein.

1/2 cup sugar
2 egg yolks
1 cup skim milk
1/4 cup unsweetened cocoa powder
1 1/2 cups half-and-half
1/2 cup bittersweet chocolate chips
1/4 cup semi-sweet chocolate chips (You could use all bittersweet or all semi-sweet depending on your preference.)
1 teaspoon vanilla extract

In a small bowl, beat the sugar into the egg yolks until it is a pretty pale yellow.
Simmer the milk in a saucepan. Add the cocoa and simmer for another 3 minutes, stirring. Slowly mix the warm milk mixture into the bowl with the eggs. If you do this too quickly the eggs will cook and you'll have scrambled egg ice cream. Mix it up well and pour it all back into the saucepan over low heat. Stir constantly for about 10 minutes until the custard thickens. If you want to be very exact about making sure the eggs are cooked, heat the mixture to 160 degrees for 3 minutes, and you'll be safe. When it's done refrigerate it while you prepare the ganache. You could just stop here and freeze the custard - it will be regular chocolate ice cream, but if you add the ganache it will be really special.
Melt the chocolate chips and the half-and-half together. Stir until the chocolate is smooth, or you could leave it a bit chunky if you want chocolate bits. Add the vanilla.
Combine the chocolate mixtures. Refrigerate until cold. Then freeze it up in the machine.