1. Blend all pesto ingredients, aside from the oil, in a food processor fitted with the “S” blade.
2. While the machine is running, slowly add the oil through the feeder and blend until a fine paste forms.
3. Cut mushrooms into halves or quarters.
4. Heat oil in a frying pan and sauté mushrooms until soft. Discard any additional juice, or reserve for use in a later recipe (see tip).
5. Add one tablespoon of pesto to the pan, or more as desired, and toss just to coat.
6. Remove from heat and serve warm or room temperature.