Gently warm oil, curry powder and cardamom in a saucepan over medium heat to 75C, add curry leaves, chilli and garlic, then set aside to cool and for flavours to infuse oil (10-15 minutes).
Meanwhile, heat a barbecue or char-grill pan to high heat and grill radicchio until lightly charred all over (1-2 minutes each side). Remove cores, separate leaves and transfer to a deep bowl. Stir vinegar into infused oil, then pour oil over the radicchio, toss to coat, then cover and marinate at room temperature for a day. Serve with grilled meat and fish, and in prego rolls. Chakalaka will keep refrigerated for up to a week.