Peel and quarter onion and place in the bowl of a food processor with a fitted blade. Dice zucchini and add to onion along with spinach and garlic. Blitz mixture until finely chopped but do not puree.

Heat olive oil in a large skillet on medium. Add onion mixture and saute with ¼ tsp each salt and pepper until softened and any water extracted during cooking has evaporated. Trasfer mixture to a plate to cool.

Preheat oven to 350°F. In a large mixing bowl add beef, pork, remaining salt and pepper, eggs, breadcrumbs, cheese and oregano. Add in cooled onion mixture and gently mix with clean hands until everything is well incorporated.

Line a rimmed baking sheet with parchment paper or aluminum foil. Scoop out meat mixture and roll into 2-inch balls. A 2-inch ice cream scoop works best, or use a tablespoon and scoop out two spoonfuls per meatball. Place onto baking sheet, about 2-inches apart. Bake for 15 minutes, then flip and bake for an additional 10 minutes. The outsides should have a nice golden brown colour.

Use meatballs in sauce for spaghetti or cool completely and freeze in a sealed container or freezer bag for use later.