Try googling vegan spinach balls, and maybe you can find similar recipe or ideas to apply to the one above? With 3 eggs, they are giving it some fluff factor not just glue. The bread *may* be enough glue, but they would be quite dense. How about doing the bread and spinach mix and stuffing it into mushrooms? Then, it does not have to stay in a ball shape and would sit int he cap, as a stuffing? if you like and can have mushrooms.