To kill the lobsters humanely, place them in the freezer for 1 hour. Remove the lobsters from the freezer and bring to room temperature.
Preheat a grill to medium.
Pour the vegetable oil in a wok and bring to up to medium heat, fry the garlic and spring onion until fragrant. Now add the crab meat, rehydrated shrimp, sugar, salt, oyster sauce, fish sauce, and chile flakes. Stir to incorporate, and then reduce the heat to a low simmer for 30 minutes, stirring every 5 minutes. Lastly add the chile oil, stir and simmer for a further 5 minutes.
You can use this sate sauce as a dipping sauce for noodle soups or add to stir-frys.
Turn the lobsters upside down on a chopping board, and slice them in half lengthwise from the tail to the top of the head. Use a sharp knife to split the claws only on the side that will be turned up on the grill.
Place each half lobster, meat side down, on the grill. Grill for 7 minutes then turn the lobster halves over and baste the lobster meat with the sate sauce and grill for a further 7 minutes.
Serve the grilled lobster with a wedge of lemon.
Refrigerate the leftover sauce in an airtight container for later use.