Tuna chiai: I just chopped into small cubes.
I sautéed a shallot (one small, finely chopped) in light olive oil for few minutes. I placed it in a metal bowl to cool before I added the other ingredients which included finely chopped parsley (3 springs, finely chopped), ginger and garlic (grated 1/2 tsp each), store-bought mayonnaise (1 tbs) and panko bread crumbs (1 tbs). I seasoned it with salt and pepper. I could have added more items such as lemon zest, hot pepper (either Tabasco or finely chopped jalapeño), but I restrained myself.
I made two equal sized patties and fried them in olive oil 2-3 minutes on both sides. I served it with mixed green and my salad dressing which is balsamic vinegar, mustard, olive oil and rice vinegar.
I was afraid that chiai may be too strong for this dish but the addition of a good amount of ginger and garlic really helped. This was a perfectly good use of scrap meat from the tuna block which would have been discarded in most circumstances.