Put the tuna with the juice and eggs in a bowl and puree (you can also puree the eggshell, it is good for the fur) you do the whole thing until everything is a pulp. Then stir in the flour (the dough will be rather dry and crunchy) Spread the dough on a tray with baking foil / baking paper approx. 2-3 cm thick. It is best to use a pizza cutter into pieces of any size and bake it for 45 minutes to 180- 190C ° ... if necessary you can leave the biscuits in there for 10 minutes longer - the harder the biscuits get, the longer they can be kept ;-)