In a large bowl, combine the bread crumbs and milk and let sit for 10 minutes.
Add remaining ingredients (ground chicken through pepper) and mix with your hands. Form into 24 balls (about 1 tablespoon each) and arrange on a baking sheet lightly greased with olive oil or cooking spray.
Preheat broiler. Broil meatballs for 5 minutes. Flip and broil for another 5 minutes.
Make the soup:
In a large pot, heat 1 tablespoon olive oil over medium-high heat. Add onion, carrots and celery and cook, stirring occasionally, until vegetables start to brown, 6-8 minutes.
Add garlic and cook until fragrant, about 1 minute.
Add chicken broth, oregano and salt. Stir and bring to a boil.
Meanwhile, cook orzo according to package directions until al dente. Drain.
Add prepared meatballs, cooked orzo and spinach and simmer until heated through, 2-4 minutes.
Season with additional salt and pepper to taste. Top with Parmigiano-Reggiano cheese and drizzle with remaining 2 tablespoons olive oil.
Notes
To make fresh bread crumbs, place a few bread chunks in a food processor and pulse to the desired crumb size. You can use almost any kind of bread; I usually have random pieces of bread in the freezer that I defrost, toast and cool before pulsing.
Recipe by Two of a Kind at https://www.twoofakindcooks.com/italian-wedding-soup/