Place the mince, ricotta, parmesan, egg, breadcrumbs, minced garlic, Italian Herbs, thyme, half the lemon zest and half of the chopped parsley in a large mixing bowl. Season well with salt and a pinch of chilli, and mix well with your hands to evenly combine all the ingredients. Roll the mixture into small balls, and refrigerate for 10 minutes.
Add a few spoonfuls of olive oil to a large, heavy-based pan over medium heat. Once hot, brown the meatballs on all sides in batches, until just cooked through – about 5 minutes each. Remove the meatballs from the pan and set aside. Adding a bit more oil, sauté the sliced onion and garlic, cooking over low-medium heat until softened, caramelised and sweet – about 10 minutes – before returning meatballs to mixture and turning down the heat to low.
Meanwhile, cook the pasta in plenty of boiling, well-salted water as per packet instructions. Once al dente, transfer the pasta to the pan along with the meatballs and a few spoonfuls of the cooking water. Add the remaining chopped parsley and lemon zest and toss to combine, coating every strand of pasta with the onion/garlic mixture. Season to taste.
Transfer to serving bowls and top with a drizzle of oil and plenty of freshly grated parmesan.