Preheat oven to 180°C fanbake. Cut pumpkin in half down the length and scoop out seeds and stringy bits. Melt a little of the butter, then brush it over cut sides of pumpkin and season with salt and pepper. Lay pumpkin buttered side down in a shallow ovenproof dish lined with baking paper. Bake for about 35 minutes, or until tender in the thickest part. Transfer pumpkin to a chopping board. As soon as it is cool enough to handle, scoop out the flesh and discard skin.
While pumpkin is cooking, peel and cube potatoes and cook gently in boiling water until just tender. Drain, reserving the water if using as stock.
Put onion and garlic in a medium saucepan with 1 Tbsp butter and 1 Tbsp water. Cover and cook gently for about 10 minutes without browning. Add potatoes, pumpkin and half the stock or potato water. Mash until thick and lumpy (or as smooth as you like), then mix in remaining stock or water. Season with 1 tsp salt, or to taste. Bring to a gentle boil, lower heat and simmer, partially covered, for 20 minutes.
For the topping, remove husks and silks from corn. Cook corn for about 10 minutes in a pot of bubbling water. Drain, cool, then slice off the kernels. If using frozen corn, put kernels in a sieve and rinse off ice crystals. Heat the rest of the butter in a medium frying pan over medium heat and add kernels (use a splatter screen if you have one as the corn tends to spit!). Cook until lightly golden, stirring often. Add chilli powder and ginger and sizzle for 1-2 minutes. Season with a pinch of sea salt.
Dish soup into bowls and top with spoonfuls of curried corn. Sprinkle with chopped mint and serve.
Pumpkin soup made with pumpkin alone can be thick, cloying and overly sweet. The trick is to add some cooked potato, which will thicken the soup without making it gloopy. The spicy corn topping on this soup is a winner.
From Taste magazine, April 2011.