Tip the rice into a large bowl and cover with cold water. Set aside to soak while you prepare the veg.
Peel and finely chop the onion. Warm a large pan over a medium-low heat for 2 mins, then add the onion with 1 tbsp oil and a pinch of salt. Pop a lid on the pan and sweat for 8 mins, stirring now and then, till the onion is soft and golden.
Trim and peel the carrots, then thickly slice them on the diagonal. Peel the sweet potato and chop it into bite-size chunks. Trim the courgette, halve it lengthways and then slice it into half-moons around 1cm thick. Peel and grate the apple.
Stir the carrots, sweet potato, courgette and apple into the onion. Crumble the stock cube into the pan and pour in 500ml boiling water. Cover with a lid, bring to the boil, then turn the heat down and simmer for 15 mins till the sweet potato and carrots are tender.
While the veg simmer, drain the rice and tip it into a small pan. Pour in 300ml boiling water and add a pinch of salt. Cover, bring to the boil and then turn the heat right down and gently simmer for 8 mins till the rice is tender and has absorbed all the water. Take off the heat and leave to steam in the pan, lid on, for 5-10 mins to finish cooking the rice.
While the veg and rice cook, make the curry sauce. Melt the butter in a small pan. Stir in 2 tbsp flour and 2 tsp mild curry powder and cook and stir for 2 mins. Add a pinch of cayenne pepper (it's spicy, so add as much or as little as you like), the tomato sauce and 1 tbsp Worcester sauce. Cook and stir for 3 mins till the paste is thick and dry. Turn the heat down very low.
When the veg are tender, scoop a ladleful of the hot stock from the pan and whisk it into the curry sauce base. Whisk till it's thick and smooth. Add another ladleful if you think it needs it. You want a thick, smooth curry paste. Spoon the thick curry sauce into the pan of veg and stir to combine. Warm through for 2 mins.
Taste the curry and add a pinch more salt if you think it needs it. Fluff up the rice with a fork and spoon into 2 warm bowls. Top with the sweet and spicy curry and serve straight away.