Heat the olive oil in a large, deep pan over a medium heat. Add the onion and cook for 5 minutes until soft and translucent.
Add the garlic and cook for 1 more minute until fragrant.
Stir in the tomato purée and honey and cook for 2 minutes, stirring often, until the purée darkens slightly.
Add the orzo and stir to coat it in the tomato mixture.
Pour in 1.2 litres of the stock, bring to the boil, then reduce to a simmer. Cook for 12 to 15 minutes, stirring often so the orzo doesn't stick, until it's tender and most of the stock is absorbed. Add the remaining stock a splash at a time if it starts to look dry.
Take the pan off the heat and stir through the mascarpone until creamy. Add the juice of half a lemon and season with salt and pepper.
Divide between bowls or meal prep containers and finish with fresh parsley and chilli flakes, if using.