Combine chocolate chips and condensed milk in a mixing bowl. Microwave for 1 minute 15 seconds. Stir gently until completely melted. Add in vanilla and stir a few more times. Pour in marshmallows and graham crackers and stir just until combined.
Transfer to a foil lined 8x8 glass dish. Spread mixture around the pan until fairly even. Refrigerate 2 hours until fully set. Cut into small squares and serve.
Once fudge is set, you can store it on the countertop.