Step 1: the sauce
- You can skip this step if you’re using shop-bought sauce; I recommend making your own though! Heat a splash of extra-virgin olive oil in a large saucepan over medium heat. Add the onion and season with a good pinch of sea salt and freshly-ground black pepper. Cook, stirring occasionally, until softened, around 5 minutes.
- Add the garlic and cook, stirring constantly, until fragrant, 30 seconds to 1 minute, then add the tinned tomatoes, water, sugar (if using) and basil. Season with sea salt and freshly-ground black pepper and stir to combine.
- Turn the heat up to medium-high and bring the sauce to a simmer then lower the heat to low, cover and cook for 30 minutes, stirring occasionally.
Step 2: the filling
- While the sauce is simmering, bring a large pot of water to the boil and season generously with salt. Add the spinach and cook until it’s just wilted, around 2 minutes. Drain well and allow the spinach to cool. Squeeze out the liquid and roughly chop the spinach.
- Combine the chopped spinach with the remaining filling ingredients in a large bowl. Set aside.
- By now, the sauce should be done. Use a fork to fish out the basil stems from the sauce. Taste and adjust seasoning, to your liking, then set aside.
Step 3: pasta and assembly
- Heat your oven to 190℃ / fan 170℃. Bring a large pot of generously salted water to the boil.
- Add the pasta and cook for 8 minutes, stirring occasionally so it doesn’t stick. You want the pasta to be very al dente as it will cook further in the oven. Drain the pasta. Run it under cold water to stop the cooking process then drain again.
- Transfer the sauce to a 3 litre casserole dish or medium roasting tin (approx. 33 cm x 23 cm) and spread in an even layer.
- Use a teaspoon or tablespoon to pack each shell with the herby spinach and ricotta mixture and arrange the stuffed shells in a single layer. Bake for 20 to 25 mins, or until golden and bubbling. Top with grated parmigiano reggiano, serve and enjoy!