Get a high-sided pan or wok on a medium-high heat to get nice and hot, and pour your stock into a small pan on a low heat to get warm. To make your fragrant soup base, add the lime leaves, chillies, garlic, ginger, lemongrass and a pinch of salt to a food processor. Chop the top few leaves off your bunch of coriander and pop to one side, then add the rest to the processor and blitz for 30 seconds or so until fairly fine. With the processor still running, add a few good lugs of olive oil, the five-spice and ground cumin. Tip this mixture straight into your hot pan, you can add a splash of stock to loosen it if you want, and fry and stir for a couple of minutes so it starts smelling fantastic. Add your sliced onion, then cook gently for 8 to 10 minutes.
Add the squash to the pan and stir well, then pour in the stock. Bring to the boil, then reduce the heat and simmer for 20 to 25 minutes until the squash is lovely and soft. At this point, add the rice and give it a really good stir. If it looks a bit dry, you can add a splash of water here. Continue to simmer for about 8 minutes until the rice is almost cooked, then add the coconut milk and bring back to the boil. Simmer for a couple of minutes until hot through and thickened a little. I like to squash up some of the squash at this point too.
Take the pan off the heat, give it a good stir, then taste and season carefully with salt and pepper. To give it a bit of twang add the lime juice – the amount you need will depend on how juicy your limes are, so keep tasting it as you go. Scatter with more sliced fresh chilli and your reserved coriander leaves before serving.
If you’re making this for a party, what I like to do is to hack the top off a massive pumpkin, scoop out the insides, then bake the shell in the oven for 40 minutes at 100ºC/220ºF/gas ¼. You can then use this as a receptacle for your hot soup, and as long as it’s an inch or so thick, it should keep warm for a good hour or so. Have it sitting out at the party with a load of little cups and bowls lined up next to it and a bunch of lime wedges, and let everyone help themselves!