In a pan put the margarine, condensed milk and chocolate. Bring to a boil, stirring constantly.
When it starts to boil, lower the heat and keep stirring until it forms a soft brigadeiro. When it starts to unglue from the bottom of the pan, turn off the heat.
With the heat off, add the cream. You can put more or less than what is indicated in the recipe, it depends on your taste, the more cream, the softer the topping will be.
Mix well and the frosting is ready to put on your cake, dessert, or wherever you prefer.