This soup with its distinctive Thai flavour is one of my favourites for autumn and, with sweet potatoes selling for around R6,99 a kilo at the moment, it’s surprisingly affordable to make. You have to work fast with raw sweet potato or it’ll quickly discolour – best peel and dice it right before you’re about to add it to the pot. Don’t be tempted to add any salt to this recipe as the stock powder and soya sauce will be ample.
1 medium onion, chopped; 1 tsp grated fresh ginger; 2 cloves of garlic, chopped; 1 tbsp olive oil and 2 tbsp sesame oil, for frying; 1 to 2 level tsp green curry paste (use less for a milder soup); 4 cups boiling water; 2 level tsp good-quality vegetable stock powder; 1 level tsp soya sauce; 1 tsp soft brown sugar; 3 dried lime or lemon leaves; 4 medium sweet potatoes (about 800g in total) plus an extra 100g (about 3/4 cup) or so of peeled, diced butternut; 1/2 tin of coconut milk, handful of fresh coriander (cilantro) leaves.
Fry the onion, garlic and ginger in the olive and sesame oil in a pot; once softened, stir in the green curry paste. Add the water, stock powder, soya sauce, brown sugar and lime leaves. Peel and dice the sweet potatoes and add to the pot. Add the diced butternut and bring to the boil. Once boiling, reduce to a simmer and cook, uncovered, until the sweet potato and butternut are tender (about 20 minutes). Don’t be fooled into thinking the liquid isn’t sufficient, as you’ll be adding some coconut milk later. Let it cool a bit, blend till smooth, then return soup to the pot. Before you turn the heat back on, add the coconut milk, shaking the tin before you open it so its contents blend properly. Stir through, then gently reheat so the soup loses its raw coconut taste (try not to boil it as the coconut milk could go all funny). Stir though the chopped coriander and serve immediately.