Prepare the meatballs: Line a tray with baking paper and preheat oven to 200ºC. In a large bowl combine the beef mince with the rest of the meatball ingredients.
Mix well to combine, then roll mixture into approx. 30 meatballs. Use a scoop to get them all the same size or simply shape them by hand.
Place meatballs onto the baking tray and place in oven for 15 minutes until browned. Set aside.
Prepare the stew: In a large pot, heat oil and fry onion for 3-4 minutes til softened.
Add the celery, carrot and leek and continue to cook for a further 7-8 minutes, stirring occasionally until the vegetables soften.
Stir in the garlic and chilli and continue to cook for a further minute.
Add the cannellini beans, orzo, chicken stock, water and crushed tomatoes. Bring to a boil then lower heat and simmer for 15 minutes until the orzo is just cooked through.
Add the baked meatballs to the pot, stir in the lemon juice and simmer for 5 minutes with the lid on.
Stir through the baby spinach and season with salt and pepper to taste.