2 oz unsweetened chocolate
1/3 cup cocoa
1 1/2 cups milk
1 1/2 cups sugar
1 tsp vanilla
1 cup heavy cream
Melt the chocolate over low heat (use a double boiler if you aren't good at this.) While it's melting, make a paste of the cocoa and half the milk.
When chocolate is melted, add the other half of the milk. Stir it in, then add the cocoa mixture. Stir until smooth, then remove from heat and let cool.
Beat the eggs until light and fluffy, then beat in the sugar a little bit at a time until the mixture is thick and creamy. Beat in the vanilla.
Stir the chocolate into the eggs, then add the cream. Chill the whole thing for a couple of hours, then freeze according to the directions for your ice cream maker.
The chocolate/milk step can be tricky, but it's worth it.