I stirred some yacon syrup (maybe 5% as much yacon syrup as unsweetened peanut butter) into some room temperature peanut butter and then refrigerated it. I think it’s as good off of a spoon as sweetened store-bought peanut butter.

Admittedly, it adds a fair bit to the cost of a jar of peanut butter – at $20 for 240 g of yacon syrup, the 38 g of yacon syrup to sweeten 750 g of peanut butter costs $3.