Creme anglaise, or English cream, is the all purpose dessert sauce. Almost any flavor can be steeped into it or introduced using extracts/liqueurs, although the traditional flavor is vanilla.
Heat cream, sugar and salt over medium heat until it is just below a boil.
Temper into lightly beaten egg yolks.
Pour everything back in the pan and cook, stirring constantly, until slightly thickened. Don't let it boil, but the mixture should coat the back of a spoon. If you're unsure, use your instant read thermometer. The mixture should be at least 160 degrees, F, but no more than 180F.
Strain into a bowl set into an ice bath.
Add vanilla (if using) and stir to chill quickly.
Notes
Steep citrus zest in the hot dairy for thirty minutes before tempering dairy into eggs. Other candidates for steeping include ground or whole coffee beans, cocoa nibs, toasted ground nuts or coconut, herbs such as mint or lemon verbena. Add a bit of bloomed gelatin (stir in while mixture is still hot--before straining) to make a thicker sauce. Add enough bloomed gelatin to make it set up like a mousse and fold in some whipped cream and, voilà: bavarian cream!