Combine breadcrumbs and milk in a large bowl. Let sit 2 minutes until fully absorbed.
Add ground chicken, egg, garlic, Parmesan, oregano, onion powder, salt, and pepper. Mix by hand for 20 seconds, just until combined.
Portion into approximately 20 balls at 25g each. Roll briefly between wet palms.
Heat 2 tablespoons olive oil in a large skillet over medium-high heat until shimmering. Add meatballs in a single layer and do not move for 3 minutes.
Turn and cook 3 more minutes. Turn once more for 2 minutes to brown any remaining pale sides. Verify internal temperature of 75°C (165°F) with a thermometer.
(Optional sauce) Remove meatballs. Add oil and sliced garlic to same pan; cook 60 seconds. Add crushed tomatoes and basil, scrape up fond, season, and simmer 5 minutes.
Return meatballs to sauce, cover, and cook on low for 5 more minutes. Rest 2 minutes before serving.