Preparation Bring stock, coconut milk, and chicken to a boil in a 1 1/2- to 2-quart saucepan, then reduce heat and simmer, uncovered, 45 minutes. Crush lemongrass stalk with side of a heavy knife (to release oils), then thinly slice. Add lemongrass, ginger, and chile to coconut mixture and bring to a boil. Remove pan from heat and let stand, covered, 30 minutes. Pour sauce through a fine-mesh sieve into a bowl, discarding solids, then return to pan and bring to a boil. Season with salt. Blend sauce in a blender until frothy, about 30 seconds (use caution when blending hot liquids). Serve immediately. Cooks' note:Sauce can be made (but not blended) 1 day ahead and chilled, covered. Reheat and blend just before serving.
Preparation Bring stock, coconut milk, and chicken to a boil in a 1 1/2- to 2-quart saucepan, then reduce heat and simmer, uncovered, 45 minutes. Crush lemongrass stalk with side of a heavy knife (to release oils), then thinly slice. Add lemongrass, ginger, and chile to coconut mixture and bring to a boil. Remove pan from heat and let stand, covered, 30 minutes. Pour sauce through a fine-mesh sieve into a bowl, discarding solids, then return to pan and bring to a boil. Season with salt. Blend sauce in a blender until frothy, about 30 seconds (use caution when blending hot liquids). Serve immediately. Cooks' note:Sauce can be made (but not blended) 1 day ahead and chilled, covered. Reheat and blend just before serving.