Place the plain flour, cornflour, cardamom, 2 tspns salt and plenty of pepper in a medium bowl.
Heat oil in wok on medium heat. Once the oil is hot (just under 180C) toss the tofu in the flour. In batches carefully lower the cubes of tofu into the hot oil and fry for 3-4 mins, turning halfway, until crisp and golden brown. Use a slotted spoon to transfer the tofu to a plate lined with a tea towel. Clean wok or get another pan for next stage.
Heat remaining 2 ½ tbspns oil in clean wok or saute pan. On high, add garlic and fry for 1-2 mins then add carrots and zucchinis and fry for 2 mins, then pumpkin stems and leaves and fry for another 2 mins.
Add the sriracha, soy sauce, lime juice and 1 tbspn water and stir until liquid is bubbling. Throw in the tofu and toss through to warm. Serve on rice.