Preheat your oven to 400°F. Thinly slice the lemon and layer it at the bottom of an oven-safe skillet. Melt butter in the skillet, add garlic, and let it sizzle until fragrant. This forms the lemony, buttery base that will flavor the meatballs as they bake.
In a mixing bowl, combine ground chicken, egg, breadcrumbs, parmesan, and seasonings. Mix gently until just combined—overmixing can make the meatballs tough. Shape the mixture into 1-inch meatballs and place them over the lemon butter base.
Slide the skillet into the oven and bake for about 25 minutes. Halfway through, spoon some lemon butter sauce over the meatballs to keep them moist. They should turn golden brown and be cooked through by the end.
While the meatballs are baking, start the orzo. In a large pot, melt butter and sauté garlic until fragrant. Stir in chicken broth, milk, salt, and pepper, then add the orzo. Cover and cook on low heat, stirring occasionally until the orzo is tender. Finish by adding spinach, lemon juice, and parmesan until creamy and smooth.
Spoon the creamy orzo onto plates or a serving dish. Place the golden chicken meatballs on top and drizzle over any leftover lemon butter sauce. Garnish with fresh parsley, lemon zest, or extra parmesan for that final restaurant-style touch.