Start by placing the chicken thigh fillets between two sheets of plastic wrap. Using a meat mallet, pound the chicken to about 0.7 cm thickness to ensure even cooking. Once flattened, season both sides generously with cooking salt, then dust the chicken with cornflour for added crispiness when frying.

In a mixing bowl, combine cornflour, plain flour, baking powder, and a pinch of salt. After blending, refrigerate the dry mixture for about 10 minutes. When ready, gradually add ice-cold soda water while whisking until smooth and well combined.

Heat vegetable oil in a heavy-based pot over medium heat until it reaches 160°C (320°F). Carefully dip each piece of the seasoned chicken into the batter, letting the excess drip off. Fry the battered chicken in the hot oil for about 3 minutes, or until it turns pale golden brown. Remove and set aside on a wire rack to cool slightly.

In a saucepan, combine chicken stock, fresh lemon juice, grated garlic, grated ginger, white sugar, and a touch of cornflour. Bring the mixture to a simmer over medium heat while continuously stirring. Allow it to cook for about 5–7 minutes until the sauce has thickened. Set it aside.

Increase the oil temperature to 200°C (390°F) for the second fry. Dip the cooled chicken again in the batter, ensuring an even coating. Fry the chicken for an additional 3 minutes, or until it achieves a deep golden color and a crispy texture. Remove and drain on paper towels.

Slice the crispy chicken into manageable pieces and arrange them on a serving platter. Generously pour the luscious lemon sauce over the chicken, allowing it to glisten enticingly. Garnish with chopped green onions and lemon slices for a vibrant finish.