Place a large pan over medium-high heat. Add the olive oil, onion, and a pinch of salt, and sauté for 4 minutes. Add the garlic and cook for a further minute.
Add the beef mince and cook for 6–7 minutes, or until no longer pink — let it sit undisturbed for 1–2 minutes first to build a crust before breaking it up.
Add the tomato paste, Italian herbs, and chilli flakes, and cook for 1 minute, mixing well. Pour in the tomato passata (with a splash of water to rinse the jar), stock, thickened cream, and orzo, and season to taste. Mix well and bring to a boil. Reduce the heat to medium and simmer for 8–9 minutes, or 1 minute less than the orzo's packet instructions, stirring occasionally.
Once the orzo is al dente, reduce the heat to low. Add the spinach and as much Parmigiano Reggiano as you like. Mix until the spinach has wilted and the cheese has melted. Check the seasoning and remove from the heat.
Serve in bowls, garnished with more Parmigiano Reggiano and chopped parsley.