Place the cashews in the barrel of a food processor and pulse for 30 seconds. Add the remaining ingredients and pulse for 15 seconds. Transfer CASHEW-GARLIC BUTTER to a small bowl and set aside while you assemble the papillotes.
In a saucepan, cook potatoes in salted water until fork-tender. Drain liquid and add mustard, red wine vinegar and salt and freshly ground black pepper. Add chopped onion, celery, eggs, heavy cream, parsley and mix well. Taste and adjust seasoning with salt and pepper. Serve alongside REDFISH PAPILLOTES.
Preheat oven to 350?F.
Season spinach with salt and pepper and divide between six 15-inch square pieces of aluminum foil. Season filets with salt and pepper and, using a flat spatula, smear both sides of each filet liberally with CASHEW-GARLIC BUTTER. Lay filets on top of spinach, fold foil pouches up carefully, and bake 20 minutes. Serve immediately, accompanied with WARM POTATO SALAD.
Yield:† 6 servings