Preheat your oven to 200°C (180°C fan) or Gas Mark 6. While it's warming, place a large, oven-safe frying pan or skillet over a medium heat. Add the olive oil and let it shimmer for a moment—you'll see the surface begin to ripple gently, releasing a clean, grassy scent.

Cook the onion until it's soft and translucent. Tip in the chopped onion and stir. It will start to sizzle, then soften, turning a pale, glistening gold after about 5 minutes. The kitchen will fill with a sweet, mellow aroma as it releases its moisture.

Add the garlic and mince. Stir in the minced garlic and let it cook for just 30 seconds until it's fragrant—your nose will tell you when. Then, add the beef mince. Break it up with a wooden spoon. It will turn from pink to a deep, rich brown, and you'll hear a satisfying, gentle sizzle. Cook for 6-8 minutes until no pink remains, and the mince has a slightly crispy edge in places.

Build the sauce. Sprinkle in the dried oregano, basil, and chilli flakes (if using). Stir for 30 seconds until the herbs release their oils and perfume the air. Then, tip in the tinned tomatoes, tomato purée, and the stock. Stir everything together. The sauce will be a vibrant, rusty red and will begin to bubble lazily. Season generously with salt and pepper, then let it simmer for 10 minutes, stirring occasionally. You'll see it thicken and reduce, becoming glossy and concentrated.

Assemble the casserole. Remove the pan from the heat. Gently nestle the fresh ravioli into the sauce, distributing them evenly. They should be mostly submerged. Sprinkle the torn mozzarella over the top, followed by the grated Parmesan. The surface will look like a patchwork of white and creamy yellow—a promise of what's to come.

Bake until golden and bubbling. Place the pan in the preheated oven. Bake for 25-30 minutes. After about 15 minutes, you'll hear a gentle bubbling sound from the oven, and the edge of the sauce will be darkening. At the 25-minute mark, look for a deep, golden-brown crust on the cheese, with some spots of darker caramelisation. The sauce should be bubbling enthusiastically around the edges. If you want an extra-crispy top, switch the oven to the grill for the last 2-3 minutes, watching it like a hawk so it doesn't burn.

Rest and serve. Remove the casserole from the oven and let it sit for 5 minutes. This is crucial—it allows the filling to set slightly, so it doesn't slide off your fork. The final dish will be a glorious, steamy, golden landscape. Scatter the torn fresh basil over the top just before serving, letting its bright, peppery scent cut through the richness.