Gribiche-like sauce for Tuna Tartare, April, 2009

1 cup rough-chopped scallions
1 cup rough-chopped cornichons
1 cup rough-chopped peeled celery
1 cup rough-chopped hard cooked egg white
1/4 cup minced chervil
1/4 cup microplaned lemon zest
1 Tbsp salt
1 tsp black pepper
2 cups xv olive oil
1 cup aioli
1/4 cup whole grain mustard

- process first 4 ingredients in robot coupe
- whisk in remaining ingredients