Eggplant And Seafood Au Gratin

Ingredients

• 6 tablespoons (3/4 stick) unsalted butter
• 1 medium-size eggplant (about 12 ounces), peeled and cubed
• 1 cup chopped yellow onions
• 1 1/4 teaspoons salt
• 1/2 teaspoon cayenne
• 1/4 cup bleached all-purpose flour
• 2 1/2 cups milk
• 1/2 pound medium-size shrimp, peeled and deveined
• 1/2 pound lump crabmeat, picked over for shells and cartilage
• 1 dozen freshly shucked oysters, with their liquor
• 1/4 cup freshly grated Parmigiano-Reggiano cheese
• 1/4 cup chopped green onions or scallions (green part only)