Bring a large pot of water to boil and arrange an ice water bath alongisde
Combine the greens (basil, chives, cilantro, scallions, and baby spinach) and blanch in boiling water until just cooked, about 1 minute. Use a slotted spoon to remove and plunge immediately into the ice bath
Drain the greens, wrap in cheesecloth, and squeeze to remove excess moisture
Boil garlic cloves until tender (about 2 minutes)
Combine the blanched greens, garlic, parmesan, and pistachios in a food processor. Puree until smooth
Gradually add the olive oil, pistachio oil, and lemon juice to the food processor to form a paste
Season the pesto with salt to taste
If using xanthan gum: weigh the pesto, calculate 0.2% of the weight, and measure that amount of xanthan gum. Whisk into pesto until fully incorporated
If not using xanthan gum: refrigerate pesto for 1 hour