Mom's Peanut Butter Fudge.
3 cups sugar
4 cups peanut butter (crunchy or creamy - chefs choice)
1 cup milk - whole preferred. Spend the dime, don't use the 2% or skim - the calories don't matter 'cause with that much sugar and peanut butter, the texture and flavor is simply more important.
Heat the sugar and milk in a large sauce pan - you'll need one with room for the peanut butter, and boiling sugar/milk bubbles up quite a bit, and you have to let it bubble for 10+ minutes, until it reaches the candy making temperature of a 'soft ball'. Stir a LOT while bringing to a boil, lower the heat and stir almost constantly while it bubbles up to a soft ball.
While you're cooking the sugar/milk candy base, heat the peanut butter for a minute and a half on high in the microwave.

eek: always use glass! Scoop it out of the plastic jar and heat it up in glass!) If needed, give it another zap, the consistency should become hot and fluid, but not glowing red like lava.
The other thing to do during the cook is to generously grease, with genuine real dairy butter, a baking pan, pie pan, cupcake dish or other shallow tool big enough to hold 4 cups of peanut butter and 3 cups of sugar, that's not plastic and suitable for handling food.
After the candy base heats to a soft ball consistency, pour/scrape the hot peanut butter into the oversize sauce pan, kill the heat and start stirring like you mean it. Use a wooden spoon, the plastic one will melt. You have to thoroughly mix the peanut butter into the candy base and get it poured / pressed into the pre-greased receptacle before it stiffens up on you. Be quick!
Semi Sweet chocolate chips can be added any time after the peanut butter goes into the candy base, when you're stirring your ass off. It helps to have a friend. Add them early to melt them in and make it true chocolate-peanut butter fudge, add them at the end or line the pan before the pour to make a chocolate chip style fudge. Leave them out if you're a peanut butter purist. That's what I love about 21st Century America.