For the sauce:
Remove stems from parsley. Reserve stems for the poaching liquid and measure 1/3 cup of firmly packed leaves. Peel the garlic and mince it together with parsley by band or in the bowl of a food processor. Squeeze 2 tablespoons lemon juice into a small bowl; whisk or process in the egg yolk, parsley mixture, 1/4 teaspoon salt and 1/8 teaspoon pepper until smooth, Combine the corn and olive oils and slowly whisk oils into the yolk mixture. (Can cover and refrigerate overnight)
For the fish:
Peel and crush the garlic and put it in a deep skillet large enough to hold the fish fillets in a single layer. Strip off the lemon zest and add zest to the skillet with the wine, 5 cups water, parsley stems, peppercorns, bay leaves, and 1 tablespoon salt. Bring liquid to a boil, lower heat, and simmer, partially covered for 10 minutes. Add garfish and simmer very slowly, partially covered, until fish is just tender at its thickest point, about 15 minutes. Cool fish to room temperature in the poaching liquid. (can set aside 2 hours at room temperature or cover and refrigerate in the poaching liquid overnight).
Remove fish from poaching liquid, cut into 1/2 inch thick slices; drizzle with sauce, serve immediately.
Cajun Country -- New Iberia, Louisiana