In a small sauce pan, melt butter over medium-high heat. Add cream and corn syrup and bring to a boil.
Remove from heat, stir in chocolate, and cover for 5 minutes. Whisk until chocolate is smooth.
Corn syrup: Corn syrup adds viscosity, sweetness, and shine to the somewhat matte, bitter chocolate. It helps to "gloss the sauce." You may also substitute maple syrup (it will change the flavor).
Chocolate: Chocolate baking bars are the best option because chocolate chips contain stabilizers to hold their shape. They also do not have as much cocoa butter, therefore the sauce will not be as luscious and smooth. However, if chocolate chips are all you have on hand, you would need 1 ½ cups chocolate chips to equal 8 ounces of baking chocolate.
Yield: This recipe makes about 2 cups of chocolate sauce.
Storage: Store leftover Chocolate Sauce covered in the refrigerator for up to 4 days.
Make ahead: The Chocolate Sauce can be made up to 3 days in advance.