Pour some clarified butter into heated frypan and add onion. Fry gently. Add garlic and simmer. Season with rosemary, salt and white pepper. Add 3/4 cup white wine and simmer gently. Add shrimp, cut side down, pressing down with small pan to keep them flat while cooking. Cook for 4 minutes then transfer to heated platter to keep warm.
Add remaining wine to pan and simmer. Strain liquid into clean pan, discarding onion and herbs and reduce on high heat to syrup consistency. Lower heat and add shrimp, then fresh butter. Increase heat and add vodka, then flame. When flame has died down, add sherry and flame again. Pour over shrimp and garnish with lemon and parsley.