Preheat oil in a deep-fryer to about 360 to 375 degrees F.
Remove biscuits from the can. Poke a hole in each one with your thumb. Form them into doughnuts. Drop them into hot grease and brown them on both sides until they were done about 2 minutes on each side. Don't forget to flip often.
For the sauce: Melt the chocolate and butter in a saucepan over very low heat. Stir in the sugar, alternating with the evaporated milk, blending well. Raise the heat to medium and bring to a boil, stirring occasionally. Lower the heat and cook, stirring, until the mixture becomes thick and creamy, about 8 minutes. Stir in the vanilla, remove the pan from the heat.
Dip cooked doughnuts immediately into the chocolate mixture before the chocolate starts to cool. Add topping/toppings of your choice.
Place the doughnuts on a plate and serve when the chocolate on the doughnuts sets, about 5 minutes.