The bubbles in the beer help the batter get poofy and delicately crisp. Think of this as a cross between tempura and British fish-and-chips.
To make it: In a small bowl, whisk together 1/4 cup soy sauce, 2 tablespoons rice or white vinegar, 1 tablespoon water, 1 tablespoon toasted sesame oil, and 1 tablespoon sugar. In 5-quart saucepot, heat 1 quart vegetable oil on medium-high until hot but not smoking (350 degrees F). Meanwhile, in large bowl, combine 1 1/4 cups all-purpose flour, 3 tablespoon sesame seeds, 1/2 teaspoon baking powder, and 1/2 teaspoon baking soda. Using fork or small spatula, slowly swirl 1 cup beer into flour, stirring until mostly combined with some sm. lumps remaining (over stirring will deflate your batter). Your oil is ready when you add a droplet of batter and it sizzles on contact instead of sinking to the bottom.
Working in batches, take a handful of trimmed green beans (you’ll need 8 ounces total) and add them to the batter, swirling them around to coat. Using your hands, while messy, is the easiest way to handle them. Pick beans up, allowing excess batter to drip back into bowl, then gently lay them in the hot oil. Cook 3 to 5 minutes or until deep golden brown, stirring frequently. It’s okay if some of the beans stick together. With slotted spoon, transfer green beans to paper-towel-lined platter. Serve immediately with dipping sauce. Continue frying next few batches. Serves 4 to 6.