Take an 8X8 square baking dish and cover it with foil. Cover the foil edges out of the dish so that it’s easy to take the baked fudge out of the dish. Lightly brush butter all over the foil.
Mix the milk, sugar, butter, and Karo Syrup in a large saucepan. Keep the flame low and occasionally stir till the butter starts to melt.
Remove the pan from heat when butter is all molten. Now mix in the peanut butter and cook it again till the mixture combines well together. Once it is all smooth, remove it from heat and let it cool to room temperature.
Next, add the powdered sugar and vanilla extract to the mixture. Use a wooden spoon to beat the mixture well until it smoothens.
Add nuts if you wish to use them in your fudge. Then, very quickly, start setting the mixture in the greased dish and put it in the refrigerator for at least 2-3 hours or until the candy is cool and firm.
Cut it into 1-inch squares, and your Old-Fashioned Peanut Butter Fudge Recipe in Karo Syrup is ready to eat!