Line an 8 or 9 inch square pan aluminium foil and brush the foil with melted butter.

In a microwave safe bowl, add the chocolate, sweetened condensed milk, butter, salt and vanilla.

Place in the microwave for 3-5 minutes, stirring every 45 seconds or so until everything has melted completely and the mixture is homogenous. You can also do this step by placing the bowl over a pot of simmering water (to create a bain-marie/double boiler) and melt the ingredients stirring every now and then. The mixture should be thick and glossy.

Working quickly, pour the chocolate mixture into the prepared pan and spread evenly.

Scatter atop the toppings (i.e. M&Ms, candy eyes, etc) if using by gently pushing them in.

Chill the fudge for an hour in the refrigerator or until firm to cut.

Cut into small squares.

Store the fudge in an airtight container or in the refrigerator, where it would last around two weeks. You can also freeze the fudge if you like