|Drain and flake tuna. Crumb 3 slices of bread and put into large bowl. Crumb 2 slices, and put on wax paper. Put Swiss cheese into blender, cover and at blend until finely grated. Add to bowl. Melt butter in saucepan. Put milk, flour and seasonings into blender and stir until smooth.|
Add to melted butter and cook over medium heat, stirring constantly, until thickened. Add tuna and set aside.
Put two eggs, parsley and onion into blender and grate until onion is coarsely chopped. Add t tuna mixture and mix briskly to blend well. Cook over medium heat about 10 minutes, stirring constantly. Add to crumb-cheese mixture, add lemon juice and mix well.
Refrigerate about 30 minutes. Put remaining egg and milk into blender and stir until well mixed. Shape about 1/2 cup of mixture into croquette, dip in egg, and roll in crumbs. Set aside while oil heats.
Fill deep fat fryer or heavy saucepan to a depth of 3 inches and heat to 325 degree. Fry croquettes until golden brown -- about 4 or 5 minutes. Drain on paper towels and keep warm in oven while frying remaining croquettes. Serve hot with tartar sauce.