Peel and chop onion, turmeric, and ginger. Set aside
Remove stalk from Thai chili pepper and cut into thirds. Set aside.
Put onion, Thai chili pepper, ginger, garlic, turmeric, and salt into a food processor and blend to a paste.
Heat olive oil in frying pan over medium-high heat. Add newly-made paste to hot pan and fry about 1 minute, stirring well. Do not use a wooden spoon; turmeric stains.
Open tin of coconut milk carefully and scrape creamy top into the paste. Stir everything together over heat for another 1-2 minutes.
Add remainder of can of coconut milk to pan. Stir in vegetable stock and canned tomatoes. Add sweet potato and squash.
Stir well and bring to a boil. Once boiling, turn down heat, put lid on, and simmer for 40–50 minutes. Start checking at 30 minutes - sweet potatoes will be soft and squash will be cooked through when done.
Remove from heat and let stand for about 10 minutes. Season as needed. Garnish with alfalfa sprouts (optional) and serve.