1. To crisp the noodles, snip into manageable lengths in a bowl and separate into four piles.

2. Heat 4cm vegetable oil in a small, deep pan and when hot, add noodles, which will puff immediately. Turn once, then remove immediately and drain on paper towel.

3. Repeat with remaining noodles.

4. Cook beans in simmering salted water for two minutes, then drain.

5. To devein unpeeled prawns, hook a bamboo skewer through the back and remove the intestinal tract. Trim off any "whiskers" from the head.

6. Heat a wok or fry pan, add two tablespoons of the frying oil and stir-fry the garlic, ginger and most of the sliced chilli for 30 seconds, tossing well.

7. Add prawns and cook over high heat for one minute, tossing well.

8. Add chilli sauce, tomato sauce, stock, salt and sugar to the pan, then bring to the boil, stirring well.

9. Simmer for two minutes or until prawns are cooked through. Add cornflour paste, stirring well, and simmer for one minute until thickened.

To serve: Add beans and serve on warm plates. Scatter with remaining sliced chilli and top with crisp noodles.