My Mum used to make me tuna fish salad sandwiches this way years ago, (far too many to count..) and as far as I'm concerned, theirs is the best and only way to make a tuna fish sandwich.
High quality canned tuna in oil is so hard to find these days, mainly tuna is flakes in brine is on our shop shelves. This is more like lumpy water, but if you have leftover cooked tuna steaks, then by all means use them instead of the canned tuna.
1 (6 ounce) can of tuna fish (if packed in water, drain it, and add a teaspoon of good quality olive oil)
1/3 cup of cottage cheese
2 Tablespoons of mayonnaise
1/4 purple onion, chopped finely
1 celery stalk, chopped finely
1 Tablespoon of capers
Juice of half of a lemon
Pinch or two of dill
2 Tbsp minced fresh parsley
1 teaspoon of Dijon mustard
(Optional - lettuce and sliced tomatoes)
Slices of bread, lightly toasted (Baguettes are great for this)
Mix all of the ingredients. Serve on toast, either open faced, or in a regular sandwich with lettuce and tomatoes.