I've come across a few different recipes for homemade chocolate sauce. This one from Smitten Kitten is by far the best I have ever found. It goes beautifully over ice cream. Or in a pinch, sit down with a jar of it and a spoon. I promise not to tell anybody.
Hot Fudge Sauce
(From Smitten Kitten)
4 oz. unsweetened chocolate
3 tablespoons unsalted butter
2/3 cup water
1/3 cup sugar
6 tablespoons corn syrup
pinch of salt
1 tablespoon vanilla
1. In a double boiler or microwave, slowly melt the chocolate and butter together.
2. Boil the water and add the chocolate/butter mixture to it.
3. Add the sugar, corn syrup, and salt. Bring just to a boil and stir until desired thickness (about 5 minutes or so.)
4. Add vanilla.
5. Store in jars in the refrigerator.
Reheat when you're ready to serve.