Once in the bowl, heat your peanut butter at 30-second intervals, giving it a stir in between each session. Be cautious when grabbing the bowl, as it may need a few seconds to cool down, and you ...

Melt peanut butter chips, Karo light syrup, butter, and vanilla in a saucepan over medium-low heat stirring until smooth, about 5 minutes. Spread 1/2 cup of the Karo mixture over the crumb base.