Place 1 inch of water in a pot with a steamer basket. Bring to a boil and add the broccoli. Steam for 5 minutes (until tender) then rinse with cold water.
Finely chop the broccoli florets. You should have about 2 cups.
Place the beaten eggs and the bread in a large bowl and mix until the bread is completely coated.
Add the grated onion, mayonnaise, cheese, lemon zest, salt, and pepper. Stir in the broccoli.
Coat the wells of 2 mini muffin pans with olive oil spray. Distribute the broccoli mixture into the muffin pans.