Soak corn cobs in cold water for 15 minutes. Heat a char-grill or barbecue over high heat. Spray corn with oil and char-grill or barbecue, turning often, for 4-5 minutes until just charred and tender. Transfer to a board. Set aside to cool. Slice kernels from cobs and set aside.

Combine corn kernels, tomatoes, onion, cucumber, coriander, chilli and ham in a large bowl. Season with salt and pepper to taste and toss to combine. Peel, halve and slice avocado lengthways and drizzle with lime juice. Add avocado to salad. Serve with lime wedges, tortillas and sour cream.