Preheat the oven to 200 degrees F (95 degrees C). Heat oil in a large skillet to 350 degrees F (175 degrees C). Line a baking sheet with foil.

While the oil is heating, whisk flour, 1 tablespoon cornstarch, and baking soda together in a shallow bowl. Whisk eggs in a second shallow bowl. Dip chicken pieces into flour mixture, then eggs, then into flour mixture again.

Working in batches as necessary, deep-fry coated chicken in hot oil for 3 to 4 minutes. Drain on paper towels.

While deep-frying the chicken, bring broth to a boil in a medium saucepan. Place cashew nuts and green onions onto the prepared baking sheet.

Add oyster sauce, soy sauce, sugar, and white pepper to boiling broth. Mix remaining 4 tablespoons cornstarch with cold water in a cup to make a slurry. Slowly stir slurry into hot broth mixture to thicken, then cook for another 5 minutes over medium-low heat.

Meanwhile, heat cashew nuts and green onions in the preheated oven for about 5 minutes.

Pour sauce over fried chicken and top with cashews and green onions.