Here is a very simple recipe for hot fudge.
4 ounces of dark chocolate chips
4 ounces of unsalted butter sliced so they are easy to melt
1/2 cup of heavy cream
1 1/4 cup of sugar
1 teaspoon of vanilla extract
Melt the chocolate chips and butter in a double boiler. Stir in heavy cream and then sprinkle in 1/2 cup sugar. Continue stirring until the sugar has dissolved. Sprinkle in remaining sugar until dissolved. Add the vanilla extract and continue to cook the fudge for another 20 minutes until it reduces a bit and get a shine.
Enjoy over your favorite ice cream. The fudge should keep refrigerated for 1 week. To reheat you can microwave for in 30 second intervals and stir in between intervals so that the fudge is heated evenly.