In a large bowl, whisk together flour, baking powder, and salt. Slowly add ice-cold water while whisking until you have a smooth batter. Add cornstarch and whisk until well combined.

Heat vegetable oil in a deep frying pan over medium-high heat.

Dip sweet potato, zucchini, bell pepper, and broccoli florets into the batter, making sure to coat them evenly.

Carefully place the vegetables into the hot oil and cook for 2-3 minutes on each side, until the tempura is golden brown and crispy.

Use a slotted spoon to remove the tempura from the pan and place it on paper towels to drain excess oil.

Repeat with the remaining vegetables until all the tempura is cooked.

Serve hot with soy sauce or sweet chili sauce for dipping.