Most everyone is happy to have a glass of sparkling wine along with a piece of cheese or a bit of caviar. But pour a glass with dinner and the same people may express surprise: Isn't Champagne an aperitif? The fact is, good bubbly is an adept partner with many different kinds of foods. Its higher acidity makes it a particularly refreshing match with rich dishes like this shellfish gratin. Furthermore, the best Champagnes and California sparkling wines particularly bruts, the driest blends of Chardonnay and Pinot Noir are full-bodied enough to harmonize with the gratin's mustard flavors. A prime example is the Veuve Clicquot Yellow Label Brut Nonvintage which happens to be one of the most popular Champagnes in the world. And with good reason: It's not often that you find so much grace and complexity in a nonvintage Champagne and its crisp citrus notes and lush yeastiness make it a natural with the gratin. If you prefer the riper, juicier California style, try the 1996 Iron Horse Classic Vintage Brut.  With its spicy apple and caramel aromas and flavors, it offers world-class depth at a good price. 

8 FIRST-COURSE SERVINGS

7 tablespoons unsalted butter
4 garlic cloves, minced
1 large shallot, minced
1 1/2 tablespoons Dijon mustard
5 cups fresh white bread crumbs
(7 ounces)
1 1/2 tablespoons chopped thyme
Salt and freshly ground pepper
1/2 cup dry white wine
2 bay leaves
3 dozen medium mussels
(1 1/2 pounds), scrubbed and debearded 3 dozen medium littleneck clams, shucked, on the half shell, empty shells reserved
3 dozen medium shrimp, shelled and deveined 

1. Preheat the oven to 500°. Melt the butter in a medium skillet. Add the garlic and shallot and cook over low heat until softened, 5 minutes. Transfer to a bowl and let cool. Stir in the mustard. Add the bread crumbs and thyme, season with salt and pepper and toss well.

2. In a medium saucepan, bring the wine to a boil with the bay leaves. Add the mussels, cover and cook over high heat until they open, 1 to 2 minutes. Transfer to a bowl; strain the cooking liquid into a cup and add a pinch of salt. Set the mussels on the half shell on a baking sheet; discard the empty mussel shells. 

3. Set the clams on the half shell on a baking sheet. Put a shrimp in each of the empty clam shells and arrange on a baking sheet. Spoon ð teaspoon of the mussel liquid over each mussel, clam and shrimp to moisten them. Mound 2 teaspoons of the bread crumbs on the seafood in each shell. 

4. Position 2 sheets of shellfish on a rack in the upper third of the oven and bake for 5 minutes, or until browned. Repeat with the third sheet. Serve. 

Variation Spread the steamed mussels and raw clams and shrimp in a large gratin dish. Sprinkle with the seasoned bread crumbs and bake at 500° until browned. Toss with cooked linguine, olive oil and some of the mussel liquid