This Cantonese ginger scallion crab recipe is inspired by the Chinese association banquets I'd go to every year with my Nin Nin (paternal grandmother), where we'd eat crab like this.
Separate crab into quarters using your hands or a knife. Hit the legs and claws with the back of a knife to crack the shell a little.
Dredge crab lightly in cornstarch and shake off excess. Heat oil on medium-high to high heat in pan and pan-fry crab until outside is crispy, and then remove. It is okay if crab is not fully cooked.
Keep 2 tbsp oil hot and discard excess. Fry aromatic ginger and white parts of scallions in oil until fragrant. Add garlic, crab, Chinese cooking wine and cover, steaming on high heat.
Mix slurry of cornstarch, 1 tbsp water, soy sauce, sugar and white pepper separately. Uncover crab and add green parts of scallions and slurry, turn down/off heat and allow sauce to thicken. Mix, salt and adjust seasonings to taste. Serve hot.
Most Cantonese ginger scallion crab recipes are pretty similar, partially due to the nature of Chinese immigration and settling, and the role of Chinese associations in helping new Chinese immigrants settle in North America. My take on it is similar to Wok of Life's Scallion Ginger Cantonese crab. If you've eaten this style of crab and are familiar with Cantonese cooking techniques, a lot of straightforward guesses can be made about ingredients and method. I hope this helps!