Pre-heat your oven to 350°F / 180°C.
Heat the olive oil in a large, shallow, heavy-bottomed, oven-proof pan over medium-high heat.
Add the onion, and sauté until translucent - about 3-4 minutes - stirring often.
Add the garlic, chili flakes, and oregano. Sauté for 1-2 minutes more.
Add the red wine and the walnuts, and stir to combine. Let the mixture simmer for one minute.
Add the pasta sauce and the baby greens. Stir to combine, and to slightly wilt the greens.
Add the ravioli, and stir it around, making sure it's all covered in sauce.
Scatter the torn mozzarella over the top.
Cover with a lid and transfer to the oven. Bake for 20 minutes.
Remove the lid, and bake for 10 more minutes, until the cheese is brown and bubbling on top.
Serve hot, with a side salad or garlic bread.