Start by spraying an 8x8 baking dish with non-stick cooking spray or lined with parchment paper.
Add the sugar and milk to a medium sauce pan and bring to a boil over medium-low heat.
Boil for 2 minutes, stirring constantly.
Remove the mixture from the heat and add the peanut butter and vanilla. Stir until fully combined and the mixture is smooth with no clumps.
Pour the fudge mixture into the prepared baking dish and refrigerate for at least 2 hours.
Cut into 16 even squares and serve.
Notes
Warm Knife: Using a warm sharp knife will help you easily slice into the fudge when cutting. Simply fill a glass up with hot water and allow your knife to sit in the hot water for 30 seconds to a minutes, remove wipe off the water and slice the fudge. Tip out the fudge out on a cutting board and let the fudge sit out at room temperature.
Even Fudge Slices: To get the perfect even squares, start by cutting in half vertically, then those halves in half, repeat on horizontally and you will have 16 perfect 2x2 inch fudge squares.
Grease Edges Well: Ensure you grease the edges of pan down well so the chocolate fudge will slide right out of the pan.
High Altitude Directions: If you live at a higher altitude, for the best fudge results, you should lower the temperature when cooking. To be more precise, reduce the temperature 2 degrees for every 1,000 feet above sea level.