Chill, uncovered, until ready to cook. In a small saucepan just big enough to hold the chicken with an inch of space at the top, combine chicken stock, coconut milk, lime juice, ginger and shallots.

Cook, stirring occasionally, until onion turns translucent, about 5 minutes. Add squash, water, a pinch of salt, sugar, coconut milk, shrimp paste, if using, and fish sauce. Increase heat to ...