Whisk the flour, cornstarch, and water in a large bowl to create a smooth batter.
Dip the chopped florets into the batter, ensuring each piece is fully coated.
Heat vegetable oil in a deep skillet over medium-high heat. Fry the battered pieces for 5 to 7 minutes until golden brown and crispy, then drain on a paper towel.
In a separate pan, warm the sweet and sour sauce mixed with soy sauce over low heat. Add the fried bites and toss gently until fully coated in the glaze.
Garnish with seeds and sliced green onions. Serve immediately over warm cooked white rice.