Place the cans, unopened, in a medium-sized pot. Pour in enough water to cover the cans, plus an inch. Cover the pot. Boil over low heat for 3 hours, rotating the cans every half hour to cook uniformly, and adding water as it becomes necessary to maintain the cans covered, (or 35 minutes over low heat in a pressure cooker, counting from the moment it starts to whistle).
Remove the cans from the water and cool to room temperature (this is a must, it is a safety issue). Once cooled, remove lid, pour the fudge into a bowl and stir to obtain a smooth cream.
Notes
To serve as a sauce, mix in a teaspoon of cold water and whisk to make it more liquid.