Start by steaming the tempeh. This removes a lot of the bitterness associated with tempeh. I do this in a pot with a little water in the bottom and a steamer basket inserted. Steam for 15 minutes.
While the tempeh is steaming place the lemongrass, garlic, green onions, red onion, chili, ginger, kaffir lime leaf, and fresh coriander in a food processor (alternatively use a mortar and pestle) and process until finely chopped.
Add the pre-steamed tempeh, the lime juice, and then soy sauce and process once more until mixed well. Transfer to a bowl and add the flour little by little until you get a consistence which easily holds the shape when shaped into cakes. Cover and refrigerate for 1/2 hour for the flavors to develop.
Heat the oil in a frying pan over medium heat. Shape the tempeh mixture into patties and sauté until nicely browned on both sides. Serve hot or at room temperature.