Famous Chocolate Sauce

This is the Bittersweet Chocolate Sauce from the cookbook California Heritage Continues, by the Junior League of Pasadena.

1/2 cup heavy cream, plain yogurt, buttermilk, or sour cream
1 cup granulated sugar
2 oz unsweetened chocolate
2 oz semisweet chocolate
1/2 cup unsalted butter
2 large egg yolks
1 tsp vanilla (at least)
1-2 tsp dark rum (optional)
1-2 tsp amaretto

In a heavy saucepan, combine the cream or yogurt and sugar. Cook over medium heat until sugar has completely dissolved, stirring constantly. Add the butter and both kinds of chocolate. Reduce the heat and cook, stirring, until chocolate is melted. Remove from the heat.

In a small bowl, lightly beat the egg yolks with a fork. Stir in enough spoonfuls of the hot chocolate mixture to heat the egg yolks from cold to warm, so they will not cook when you pour them into the saucepan. Add the egg mixture to the chocolate mixture gradually, stirring constantly. Cook gently over low heat for 3 minutes, stirring continuously. Remove from the heat.

Stir in vanilla and the rum and amaretto until well blended. Store in the refrigerator until ready to serve.