In a mortar, combine the lemongrass, ginger, shallots, and garlic; pound to a semismooth paste. Stir in the oil, oyster sauce, fish sauce, turmeric, and the 1/3 cup coconut milk and mix well. Reserve 1/4 cup of this mixture and set aside. Transfer the rest to a large mixing bowl and add the short ribs. Toss the ribs to coat, cover the bowl, and let them marinate in the refrigerator for 24 hours (you can get away with marinating for 6 hours at a minimum, though the satay will have less depth of flavor).

When it is time to cook the ribs, preheat your grill until very hot. I highly recommend cooking satay on an outdoor grill over charcoal briquettes, but gas will suffice (cook them indoors in a grill pan only if you have a very good exhaust system, since they generate a lot of smoke). Make the baste by mixing the reserved 1/4 cup marinade with the 1/3 cup coconut milk. Grill the ribs for about 2 minutes on each side (a little more or less, depending on how you like your meat). As they cook, brush the ribs with the basting liquid and a sprinkling of salt. Let the cooked ribs rest for 2 minutes before serving with the satay peanut sauce and cucumber ajat. Accompany with jasmine or sticky rice or slices of toasted white bread.