Start by lining an 11 x 7 inch glass baking dish with parchment
In a heavy bottom sauce pan dump 1 can sweetened condensed milk, the semi-sweet chips, and 1 tsp peppermint extract and turn on to a low heat. Do not turn it too high or you may burn your fudge.
Let the mixture heat, stirring regularly. When chocolate is fully melted, and well incorporated, remove from heat and pour into lined baking dish. Usually takes 5-8 minutes over heat to reach this point, but every stove top is different. Just be sure to stir well, and if you notice the chocolate is heating too much and getting thick and crumbly, turn the heat down.
Pour into lined baking pan. Garnish with peppermints
Let the fudge set up (at least 1 hr, or speed it up by putting it in the fridge)