Cut up all the vegetables and meats into bite-sized pieces.
Fold the kaffir lime leaves in half, and take out the veins. (This makes the leaves more fragrant.)
Put 1 to 2 tablespoons of vegetable oil and the jar of green curry paste in a frying pan over low heat.
Stir fry the paste slowly while mixing with the oil. It burns easily, so pay attention. Cook for about 5 minutes. It will start to smell very fragrant.
When the paste is well cooled, pour about 1/3 of the top of the coconut milk (the thickest part) into the frying pan, and simmer over medium heat.
When the oil comes to the surface (separation), add the vegetables and protein and stir fry quickly. Add the remaining coconut milk and the kaffir lime leaves.
Simmer briefly. Fill the coconut can halfway with water, and add the water to the pan. Season with fish sauce and sugar.
When the solid ingredients are cooked through, the curry is done. If the flavor is lacking, adjust with fish sauce. Be sure to simmer over low heat only from Step 6 on. The separated oil will become incorporated again.
We usually add chicken and eggplant, or pork and kabocha squash, plus maitake or shimeji mushrooms.
If you think it needs more flavor, drizzle on some fish sauce.
Story Behind this Recipe
I adapted a recipe that I saw on a jar of commercial green curry paste.
Stir-fry the green curry paste patiently, to draw out its fragrance. The coconut milk in the can is separated into the thick, creamy part and the thin watery part, so don't mix it together before using. Make sure to stir-fry well to draw out the oil. Once you add the remaining coconut milk, turn the heat down to low.