Hi Katie,
Every parrot is a bit different when it comes to food. Each will develop their own preference. Mine prefer their food cooked. So, that being said, I bought a steamer
to cook veggies in rather than boil (where vitamins are lost in boiling and birds need their vitamins). You mentioned asparagus, just use the tips, not the stalk, the stalk is too stringy for their digestive track and can cause quite a bit of discomfort for the parrot. Same goes with celery, don't give them that, it also is stringy. Ice berg lettuce is not good, and avocadoes are poisonous to a bird. Beans and lentil should always be cooked.
I make corn-bread balls and add sunflower seeds, dates, raisins, pellets (as they hate plain pellets) and cook it in with the corn-bread. They love that for their breakfast with some plain stone ground cooked oatmeal. Yum yum, I really like it my Blue fronted amazons says out loud.