First cook the quinoa in about 1/2 liter of salted water, according to the instructions on the package, then drain, and let it cool well before using.
While the quinoa cools, wash all the vegetables, chop finely (excluding the peas, which you can leave whole) and sauté them in a little olive oil.
Mix the quinoa with the sautéed vegetables, the minced parsley, the grated cheese, and the eggs, then season with a little salt and pepper.
Add the breadcrumbs only at the end if necessary: the dough must be moist but not wet, otherwise the meatballs may crumble during cooking. Form with the meatball or croquette shapes by hand, and heat about an inch of olive oil to cook the meatballs until fully browned.
The meatballs must form a thin crust, thus be careful to turn them gently so as not to break them.
Serve hot or cold, with a nice fresh salad as a side dish.