Saute garlic and onion until onions are soft, then add tuna, salt and black pepper.
When cooked, add mashed potatoes and milk and stir cook until the mixture is almost dry.
Then add butter and green onion and mix very well.
Shape into oval croquettes then roll in lightly beaten eggs (egg wash) and then in bread crumbs.
Roll again in egg wash and breadcrumbs then deep fry in hot lard or cooking oil until golden brown.
Serve hot and arrange in a bed of lettuce.
You can use mayonnaise or sweet and sour sauce as dipping sauce.