Cook the broccoli: Steam or boil the broccoli until tender. Drain thoroughly and allow it to cool slightly.
Remove excess moisture: Pat the cooked broccoli dry or gently press it with paper towels to remove as much moisture as possible.
Chop the broccoli: Finely chop the cooked broccoli into small pieces. Avoid turning it into a puree.
Combine the ingredients: Add the broccoli, cheddar cheese, Parmesan cheese, breadcrumbs, egg, garlic, onion, Italian seasoning, salt, and black pepper to a large mixing bowl.
Mix: Stir everything together until the ingredients are evenly combined and the mixture holds together when gently pressed.
Shape the balls: Scoop out portions of the mixture and roll them gently between your palms to form compact balls. Place them on a parchment-lined baking sheet.
Prepare for baking: Lightly brush or spray the broccoli cheese balls with cooking oil.
Bake: Bake in a preheated 400°F oven for about 18–20 minutes, turning them halfway through, until golden brown and crispy.
Rest: Remove from the oven and allow the broccoli cheese balls to rest for a few minutes before serving.
Serve: Serve warm with ranch dressing, marinara sauce, garlic aioli, honey mustard, or your favorite dipping sauce.