Tempura avocado and prawns

Ingredients

• 3/4 cup plain flour, plus 1/2 cup extra, for dusting
• 1/2 cup cornflour
• 1/2 teaspoon bicarbonate of soda
• 1 egg, lightly whisked
• 250 millilitre soda water, chilled
• 2 avocados, stoned, peeled, cut into thick wedges (1.5cm)
• 250 gram green prawns, peeled, deveined, tails on
• 1 red capsicum, seeded, cut into 2cm-wide slices
• 2 ice cubes
• vegetable oil, to deep-fry
• soy sauce, lime wedges, to serve