Preheat barbecue until medium-hot.
For the Chipotle Cream, mix together all ingredients in a small blender or food processor until the sauce is smooth and creamy. Taste and adjust seasoning and spice level as desired, adding more sour cream or chilli accordingly. Set aside in the fridge until ready to use. The sauce will thicken after chilling.
Heat a small pan over a high heat and dry roast the cumin and coriander seeds until they start to pop. Grind to a powder and mix together with the salt and pepper.
Rub the chicken breasts with the olive oil and coat evenly with the spice mixture. Cook the chicken on the preheated barbecue for about 10 to 12 minutes, depending on thickness, turning half way through. Check the breasts are fully cooked with a meat thermometer (they should have an internal temperature of 74 at the thickest part), but take care not to overcook.
Add the lime halves to the barbecue with the chicken, cut side down, and cook until charred but not burnt. Set aside when done.
Set the chicken aside to rest for 5 minutes, then shred into large pieces with two forks.
While the chicken is resting, heat the tortillas on the barbecue for about 30 seconds each, placing them in a brown paper bag or clean tea towel to keep warm.
To serve, divide the chicken evenly among the tortillas. Top with a good dollop of Chipotle Cream, salad greens, red onion and jalapeños to taste. Serve the charred limes alongside for a burst of smoky zing.
A delicious summer stunner with plenty of warm, tasty spice but not too much heat. Perfect with a long, cool glass of Wolf Blass Silver Label Chardonnay.