To make the curry paste, roughly chop the chilli, garlic, ginger, lemongrass and onion or shallot. Pound in a mortar and pestle until reduced to a pulp* (see tip). Heat oil in a heavy-based saucepan and fry paste until fragrant and browned. Stir to prevent catching. Add fish sauce and stock and bring to a simmer.

Add duck legs and simmer gently for 1½ hours.

Skim fat off the top. Add eggplants, snake beans and lime leaves and cook for three minutes.

Serve with Thai or holy basil and rice.

*Tip: The traditional way to make a Thai curry paste is in a mortar and pestle. Add ingredients one at a time, pounding each item to a fine pulp before adding the next. Start with the hardest ingredients and end with the softest. Pounding releases the fragrance of the ingredients and allows you to adjust the recipe as you go. It gives a superior result but takes a long time. Alternatively, you can blend ingredients with a stick blender, adding a little water or oil to help the process or pass ingredients through a mincer several times until you achieve a fine paste.