Line an 8-inch x 8-inch baking pan with parchment paper. Lightly oil the paper with coconut oil. Set aside.
In a medium saucepan, add chocolate chips or chocolate pieces and top with condensed milk.
Bring to low-medium heat, stir until the chocolate is melted and a shiny, thick mixture forms.
Pour and spread evenly into the prepared baking pan.
Keep 3 hours at room temperature, or overnight, to firm up. You can also firm up the fudge in the fridge in 30 minutes, but it loses its shine, so I prefer room temperature.
Cut into 16 squares and store in a cool place in the pantry, in an airtight container. This fudge doesn't need to be refrigerated. But you can also store the fudge in the fridge if it's hot where you live, but its texture won't be as soft and chewy. Bring to room temperature 1 hour before eating for the best texture if you choose to store your fudge in the fridge.