Heat the oven to 180 C / 350 F.

Warm 3 tablespoons of olive oil in a large oven-safe baking dish or Dutch oven over medium heat on the stovetop. Add the diced onion and cook for 5 minutes, stirring occasionally, until softened and translucent.

Add the sliced garlic and tomato paste and cook for 2 minutes, stirring constantly, until the paste darkens slightly and the garlic is fragrant.

Add the rinsed pearl barley and stir to coat it in the oil and tomato paste mixture for about 1 minute.

Pour in the crushed tomatoes and vegetable broth. Add the dried oregano, thyme sprigs, chili flakes if using, salt, and black pepper. Stir everything together until evenly combined.

Bring the mixture to a gentle simmer on the stovetop, then remove from the heat. Cover the dish tightly with a lid or two layers of foil.

Transfer to the oven and bake covered for 60 minutes, until the barley is nearly tender and most of the liquid is absorbed.

Remove the foil or lid and bake uncovered for a further 15 minutes, until the top is lightly caramelized and the remaining liquid has reduced to a saucy coating around the barley.

Remove from the oven. Discard the thyme sprigs. Stir in the grated Parmesan if using and taste for salt.

Finish with a drizzle of extra virgin olive oil and a handful of chopped flat-leaf parsley before serving.