First, you want to check that there’s no mold in your granola since moisture can lead to a buildup of mold.
Preheat the oven to 400 degrees.
Line a baking tray with foil and spread the granola out onto the foil.
You want a thin layer of granola. You might need two baking trays if you have a lot of granola to crisp up.
Bake for up to 5 minutes and then leave to cool.
Once cool, the granola should have crisped up nicely. If you live somewhere particularly humid, it’s best to let the granola cool inside the oven where it’s dry. This prevents the humidity from ruining the granola before you get a chance to eat it.