Heat a couple of tablespoons of oil over medium-high heat. Add curry paste, smushing a bit to break up. Add pork and onions. Cook for a couple of minutes, stirring periodically. You’re not trying to thoroughly cook them, just get them started.
Add coconut milk, potatoes, brown sugar, and peanuts (if using). Bring to a boil, then reduce heat. Simmer for about 20 minutes, or until potatoes are tender.