How to Make It
In a food processor, chop the garlic. Add the basil, parsley and mint and pulse until chopped. Add the nuts and oil and pulse until a smooth paste forms. Add the butter and cheese and pulse until incorporated. Season with salt.
Spoon the pesto into five 1/2-pint canning jars or airtight plastic containers. Tap lightly on a flat surface to release any air bubbles. Pour 1/2 inch of olive oil on top of the pesto. Seal the jars and refrigerate for up to 2 months or freeze for up to 6 months.