1) In a large wok, heat the oil over medium-high to 185C.
2) Meanwhile, season 280g of the flour with salt and freshly ground black pepper. Dredge the shrimp in the seasoned flour.
3) In a large mixing bowl, whisk the remaining 560gof flour with the egg yolks and soda water. Hold the prawns by their tails dip them into the batter.
4) Working in batches, fry the prawns in the hot oil, turning them once, until they are golden brown, about 3 minutes per batch. Remove the prawns from the oil and drain them on paper towels. While they are still hot, sprinkle the prawns generously with salt and freshly ground black pepper. Transfer the prawns to a serving tray.
5) When the prawns are cooked, carefully pour off all but 125ml of the oil. Add the garlic, ginger, green onions and jalapeno and fry until crispy. Spoon the seasoning over the prawns and serve immediately accompanied by lemon wedges.