Start by boiling both sugars, butter, and milk in a pot until it reaches 236 degrees then immediately stop.
Add in peanut butter and marshmallows and whip until it starts to thicken.
Pour into a buttered 8″ x 8″ pan. You could also line with parchment paper to make it even easier to take out if you’d like to.
It takes about one to two hours for the fudge to harden completely. Wait until cooled to room temperature and slice into squares.
Notes
It is not recommended to double this recipe. Candy recipes require precise temperatures, and with double the ingredients, getting the batch to the correct temperature is tricky without burning or scorching the bottom.Use an accurate candy thermometer.A wooden spoon is the traditional utensil for a reason, but a high temperature rated silicone works well, too.Gather your ingredients and prep the pan before you start cooking. Candy is a fast process and requires your full attention.