Basic Curry Sauce

3 tablespoons vegetable oil or ghee (clarified butter)
1 medium onion, finely chopped
4 cloves garlic, peeled and sliced
1 1/2-inch piece ginger, peeled and thinly sliced
2 mild fleshy green chiles, de-seeded and veined then chopped
1/2 teaspoon turmeric powder
1/2 teaspoon ground cumin seed
1/2 teaspoon ground coriander seed
1 tablespoon tomato paste mixed with 4 tablespoon water

Heat the oil in a heavy pan then add the chopped onion and stir for a few minutes over high heat. Add the ginger, garlic and green chiles. Stir for 30 seconds then turn the heat down to very low. Cook for 15 minutes, stirring from time to time making sure nothing browns or burns.

Add the turmeric, cumin and coriander and cook, still very gently, for a further 5 minutes. Don't burn the spices or the sauce will not taste good - sprinkle on a few drops of water if in doubt. Remove from the heat and cool slightly.

Put 4 ounces cold water into a blender. Add the contents of the pan and blend until very smooth. Add the tomato paste and water, then stir.

Put the pureed mixture back into the pan and cook for 20 to 30 minutes (the longer the better) over very low heat stirring occasionally. You can add a little hot water if it starts to stick to the pan but the idea is to gently "fry" the sauce which will darken in color to an orange-brown. The final texture should be something like good tomato ketchup.

NOTES: This is the basis for many of the restaurant-style curries. The recipe makes between 8 and 9 fluid ounces of sauce which is enough for 2 main course curries or a main course and some side dishes. The recipe doesn't work as well if you try to make a smaller portion. It will double nicely if you're making a number of curries but you will need to extend the cooking time a bit. If you have some sauce left over it will keep in good condition in the freezer but only for a few weeks. Even small amounts are useful for making a quick one-portion curry. It goes a long way.