Line an 8 x 8 baking pan with parchment paper. In a large microwave-safe bowl, combine chocolate and condensed milk. Microwave for about 30 seconds and remove and stir until chocolate is mostly melted. Microwave again for another 30 seconds and stir again. Repeat again for another 30 seconds. Chocolate should be completely melted and smooth. Careful not to overheat in microwave. Add in peppermint extract and mix again until smooth.
Pour fudge into pan and spread evenly across. Add four drops of red food coloring near the four corners of the pan. Using a fork, make figure 8's in the fudge until red food coloring is mixed in and you have swirls of red throughout. Place in fridge for several hours to set. Cut with sharp knife into bite-sized squares.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.