Gather a medium saucepan and a spatula, making sure they're clean and ready for your chocolate adventure.

In your saucepan over low heat, mix together the sweetened condensed milk, butter, and chocolate chips. Stir continuously until the mixture is melted and silky smooth, about 5-7 minutes.

Remove the saucepan from the heat, and stir in the vanilla extract.

Line a baking pan with aluminum foil for easy removal, then pour your delicious mixture into the pan, spreading it evenly with the spatula.

Place the pan in the refrigerator and let your fudge chill for about 2 hours or until firm.

Once chilled, lift the fudge out of the pan using the foil edges, and slice it into squares or rectangles to serve.