1. Pat oysters dry with paper towels; dredge in flour, shaking off excess. Dip each oyster in egg; coat with breadcrumbs.
2. Melt 2 tablespoons butter in a large nonstick skillet over medium heat; add oysters. Cook 2 minutes on each side or until golden; drain on paper towels, and keep warm. (Do not wipe out skillet.)
3. Melt remaining 2 tablespoons butter in same skillet over medium-high heat; add shallots and mushrooms. Cook 4 to 5 minutes or until tender. Add sherry, scraping any brown bits from bottom of skillet; simmer 1 minute. Add cream; simmer 2 minutes. Add turkey and next 3 ingredients. Simmer 2 to 3 minutes or until turkey is heated through and sauce thickens. Spoon mixture over toasted croissant halves, and top with oysters. Garnish, if desired.
*For testing purposes, we used Panko breadcrumbs.