1 quart shucked oysters
3/4 cup butter, divided
2 medium onions, chopped
1-1/2 cups chopped celery
1/2 cup all-purpose flour
2 cups half-and-half cream
2 teaspoons minced fresh parsley
1 teaspoon salt
1 teaspoon minced fresh thyme or 1/2 teaspoon dried thyme
1/4 teaspoon pepper
1/8 teaspoon cayenne pepper
4 large egg yolks, lightly beaten
2 cups crushed Ritz crackers (about 50 crackers)
Lemon slices
Fresh thyme sprigs
1. Preheat oven to 400°. Drain oysters, reserving oyster liquor; set aside. In a large saucepan, heat 1/2 cup butter over medium heat. Add onions and celery; cook and stir until tender, 4-6 minutes. Stir in flour until blended; gradually whisk in cream. Bring to a boil, whisking constantly; cook until thickened, about 2 minutes.
2. Reduce heat; add next five ingredients and reserved oyster liquor. Cook and stir until smooth, about 2 minutes. Remove from heat. Stir a small amount of hot liquid into egg yolks; return all to pan, stirring constantly.
3. Pour half of sauce into a greased 13x9-in. baking dish. Top with half of oysters; sprinkle with half of cracker crumbs. Repeat layers. Melt remaining butter; drizzle over top.
4. Bake, uncovered, until golden brown, 23-28 minutes. Let stand 10 minutes. Serve with lemon slices and thyme sprigs.
TOTAL TIME: Prep: 20 min. Bake: 25 min. + standing YIELD: 6 servings.