In a large pot or a very deep pan, drizzle some olive oil over medium heat. Add the onion and allow to cook for 5 minutes until translucent and fragrant.
Add the garlic and fresh ginger and sauté for 1 minute, then add all the spices and cook for another minute.
Add the butternut (that has been peeled, deseeded and cubed) and the chopped carrots. Stir well into the spices to coat all the pieces and allow to get browned slightly - turn up the heat if necessary.
Pour over the stock and maple syrup/sugar and allow the pot to simmer for 40 minutes, stir occasionally. The stock will cook down, add a little water if needed. You are looking for a rich, thick sauce coating the butternut and carrots.
Scatter torn coriander leaves and the lemon zest before serving hot. Serve over rice or couscous if desired.