For two small servings to accompany sake, I used bitter melon (1/2), firm tofu (1/3), and egg (1, beaten). I did not use Spam as called for in the recipe (my wife absolutely prohibits me from even mentioning the name because of her childhood experience while at summer camp where they served spam literally for breakfast, lunch and dinner--too much of a good thing). Instead I used another pork product; thinly sliced leftover roasted pork tenderloin (5-6 slices). I suppose, in an authentic Okinawan recipe, some kind of salt preserved pork is used but Spam has been also popular there (due to American military influences).
Bitter melon: I cut it in half lengthwise and scoped out the inner "guts" (seeds and whatever around them) using a teaspoon. I sliced the halves into 2-3 mm (1/8 inch) thickness (It can be thicker if you like). I salted, mixed and let stand for 30 minutes. I washed them in water and squeezed out the excess moisture by wringing the pieces in a paper towel. This process reduces the bitterness but if you like the bitter taste skip this step.
Tofu: I wrapped it in a paper towel with a small plate on the top as a weight and let it sit on the cutting board for 30 minutes, so that the water content is reduced. I cut the tofu in half to increase the surface areas.
In a non-stick frying pan on a medium flame, I added dark roasted sesame oil (1 tbs) and the tofu cubes without crumbling them. I fried them for 5 minutes on each side or until the surface browned. I moved the tofu to the side of the frying pan and added the bitter melon slices and stir fried for 2-3 minutes. Then I added the pork. I took the tofu I just browned, crumbled it and continued to stir fry it together with the other ingredients for another minute or two. I seasoned with salt, pepper, and soy sauce (1/2 tsp, optional). I added the beaten egg next and stirred. When the egg was cooked, I remove the dish from the heat.
This is a very homey comforting dish and the slight bitter taste of "goya" is rather unique. This will go well with any drink but especially with sake or maybe with "awamori" 泡盛 (not for us though).