Let’s get cooking.
Heat the oven to 180°C fan or 200°C conventional. Set out a baking dish about 30 × 20 cm, deep enough to hold the pasta and sauce. Cut the 500 g chicken into 2 cm pieces, chop the onion and deseeded pepper, mince the garlic and grate the cheddar.
Heat the 1 tbsp olive oil in a large deep frying pan over medium-high heat. Add the chicken and cook for about 4–5 minutes, turning, until lightly golden outside. It will finish cooking in the sauce.
Add the onion and pepper. Reduce to medium heat and cook for about 5 minutes, stirring, until the onion starts to soften. Stir in the garlic and 1 tsp ginger paste and cook for 1 minute.
Pour in the 500 g pasta sauce. Bring to a gentle bubble, then lower the heat and simmer for 10 minutes, stirring occasionally. Add a small splash of water if it starts catching on the bottom.
While the sauce simmers, boil the 300 g pasta for 2 minutes less than its packet cooking time. Before draining, scoop out 100 ml of the pasta water into a mug. The pasta should still be firm because it will finish in the oven.
Stir the 150 g cream cheese into the sauce over low heat until no lumps remain. Add the reserved pasta water a little at a time until the sauce coats a spoon but is loose enough to mix easily; you may not need all of it.
Stir in the drained pasta and 150 g spinach until the leaves wilt. Add the black pepper and, if using, the oregano and chilli flakes. Transfer to the baking dish and spread evenly.
Scatter the 150 g cheddar over the top. Bake for 15–20 minutes, until golden and bubbling in the centre as well as at the edges. Check that the centre of a large chicken piece reaches 75°C for 30 seconds. Rest for 5 minutes before serving.
