If you’re patient about getting your hands on thawed out peanut butter, you can wait until it has properly thawed over time in the refrigerator.
As the peanut butter starts to thaw the oils will separate from the solids in the peanut butter, in a process known as syneresis. Putting the peanut butter in the refrigerator to thaw helps to slow this process down.
When the peanut butter naturally becomes soft enough to stir in the refrigerator, you can give it a really good stir for several minutes. This stirring can help to restore the peanut butter to the very same consistency and texture that it had when you first bought it.
You can still achieve this effect without the refrigerator but it would require a lot more stirring, and is not the recommended method.
We strongly advise against defrosting peanut butter in the microwave, because the heat will cause the oils in the peanut butter to burn, which can have health implications