Squeeze water out of tuna or allow to drain in sieve for 10 minutes. Mix first four ingredients together thoroughly (don't worry if it is a little wet). Place cracker crumbs in flat plate or on waxpaper. Form three or four football shaped lumps and throughly coat each with the crumbs. Squeeze gently to bring the egg out and make the crumbs adhere better. Put oil and butter into medium frying pan and bring to medium heat. Place the croquettes into pan and cook slowly until golden brown. The sides will flatten out while cooking. You can make them 3 sided or 4 sided but don't turn too much as they are fragile.