It doesn't get much more basic than this, guys.
About half a cup of water. A tablespoon of castor sugar. And 50g of good dark chocolate.
Melt the sugar in the water. Add the chocolate, and stir till melted. Take off the heat and serve immediately over icecream or chocolate sponge cake.
It's not as thick as I like my chocolate sauce usually, but it does the trick.
Talk about basic.