Heat the olive oil and butter in a large frypan over a medium heat. Add the onion and cook gently for 4 to 5 minutes, until softened and fragrant.
Add the garlic and sauté for about a minute, stirring often.
Add the oregano and chilli flakes and cook for a further minute, allowing the flavours to open up.
Stir through the sun-dried tomatoes and Dijon mustard, then add the risoni and stir to coat it in the mixture.
Add 2 cups of the stock and cook, stirring from time to time, for about 5 minutes. Add the remaining stock along with the cream and continue cooking for a further 5 to 7 minutes, or until the risoni is tender and the mixture is creamy. If needed, add a little extra stock or water to loosen.
Stir through the lemon juice and parmesan, then add the spinach, allowing it to wilt gently into the dish.
Finish with the lemon zest and taste to season. Adjust with sea salt and freshly cracked black pepper. Serve warm, with a little extra parmesan if you like. Lovely with a simple green salad.