Prepare a 9x13-inch baking pan greasing or lining with parchment paper or wax paper.
Add the sweetener, butter, and evaporated milk to a large saucepan. Heat over medium heat to a boil.
Reduce heat to maintain the boil without overheating, and stir constantly for 4-5 minutes. Alternatively, you can heat the mixture to 234 degrees Fahrenheit, but 4-5 minutes should be sufficient if you don't have a candy thermometer.
Remove from heat.
Quickly add the chocolate chips, marshmallow cream and vanilla extract to the saucepan and stir until smooth.
Pour the mixture into the prepared pan.
Let the fudge set for at least 3-4 hours at room temperature, or place in fridge for faster cooling and a firmer result.
If you chose not to use paper or foil, when firm, simply cut the fudge into small pieces in the pan.
If you did choose to use a baking pan liner, when firm, lift the entire block of fudge using the edges of the paper or foil, placing the block on a cutting board. Cut into serving-size pieces.
Store the fudge in the refrigerator for longer shelf life.