In a medium frying pan over medium heat,add 30 millilitres of oil,onion and garlic. Season and cook for five minutes until soft and golden,then tip into a bowl to cool.
In a food processor,add the mince,sausage meat,eggs,one tablespoon oregano,lemon zest and black pepper and blend to a paste. Add breadcrumbs and whiz again to combine. Tip into a bowl,add parmesan and parsley and mix well. Roll into small balls about the diameter of a 20-cent piece.
Place a large,heavy-based pot over medium heat,add 30 millilitres of oil and brown a batch of meatballs for three minutes on all sides. Remove from pan and set aside. Repeat process until all meatballs are cooked.
In the same pot,wipe out leftover oil,add remaining 20 millilitres oil and cook garlic for two minutes or until golden. Add stock,tomato sugo,sugar,remaining oregano and polpetti and bring to a simmer over a medium heat. Reduce heat to low,cook for 20 minutes and check seasoning. Stir sauce through your favourite pasta and serve.