Cut onions in small pieces. Mince galric. Saute in olive oil until yellow. Add shrimps in shells. Let simmer 5 minutes. Add wine, according to taste. Season with salt and pepper; simmer 10 more minutes over moderate heat. Remove shrimps from sauce with slotted spoon. Shell and save. Stir in tomatoes and tomato paste and cook 5 minutes over moderate heat. Mash everything together with potato masher. Add broth and simmer slowly for an hour, until sauce is very thick. When ready to serve return shelled shrimps to sauce, add parsley and butter. As soon as butter melts it is ready to serve. Good on rice or pasta. Serves 4.