Peel and finely slice the onion. Put a deep frying pan or wok on a medium heat. Warm up for 1 min. Add 1 tsp oil, the onion and a pinch of salt. Cook for 5 mins, stirring now and then, till the onion is starting to soften.
Crush 4 cardamom pods in a mortar and pestle to break them open (or pop them in a bowl and bash with a rolling pin or jar). Discard the green papery skins. Keep the black seeds. Halve the chilli. Scoop out the seeds and white pith and finely chop it.
Add the cardamom seeds and chilli to the onion with 2 tsp curry powder and another 1 tsp oil. Cook, stirring, for 1-2 mins to warm the spices.
Dissolve the stock cube in 300ml boiling water and add to the pan. Pour in the rice. Cover with a tight-fitting lid – if you don’t have a lid, cover with a baking tray. Bring to a simmer and gently cook for 10 mins.
Take off the lid and sit the haddock fillets on top of the rice. If it looks dry, add a splash more water to the pan. Cover, lower the heat and cook gently for 5 mins, or till the fish flakes when pushed with a fork, and the rice is just cooked.
While the haddock cooks, grate the courgette. Pop it in a sieve and press down with a wooden spoon to squeeze out any moisture. Stir the courgette with the yogurt and a pinch of sea salt. Set aside.
Shred the spinach leaves, discarding any really thick stalks. Add the spinach to the pan and gently stir everything together over a low heat for 1-2 mins to wilt the spinach and break up the haddock fillets.
Trim the root off the spring onion and finely slice it. Divide the kedgeree between 2 warm plates. Top with the sliced spring onion. Serve with the courgette yogurt.