This is a versatile sauce that can be used in many ways. It can be used on pasta, vegetables, or as a barbecue sauce. If thinned with water, it can be used to poach fish or chicken. With vinegar added, it can be a salad dressing. It can also be made ahead and frozen. I've substituted red New Mexico chili powder for piment d'espelette; if you can get piment d'espelette, by all means use that. You can also substitute hot paprika. Adapted from The Basque Kitchen.