Tabasco sauce is sometimes added, and parsley is sometimes used as a garnish. Worcestershire sauce, salt and pepper, white wine, lemon juice, and shallots or onion are also used. Other basic ingredients include butter, peppers, bacon and garlic. The dish uses littlenecks or cherrystone clams. It is often served as an appetizer in New England and is served in variations nationally. It originated in Rhode Island in the United States. Green peppers are also a common ingredient. Clams casino over rock salt with lemon and parsley garnishĬlams casino is a clam 'on the halfshell' dish with breadcrumbs and bacon.