Blanch the corn cobs in boiling water for five minutes and refresh under cold water to stop the cooking process. Set aside.
For the spice rub. grind the cumin and pumpkin seeds together in a mortar and pestle. Add the chipotle powder, smoked paprika, cayenne, salt and lime zest and mix together.
To make the mayonnaise, finely chop the chipotle and add to the mayonnaise, yoghurt, lime juice, oregano, sea salt and pepper. Stir to combine.
Brush the corn cobs with oil and char-grill until lightly charred. Remove from heat and roll in the Chipotle mayonnaise and then roll in the grated cheese and sprinkle with the spice mix. Serve immediately.
Keep any left over chipotle mayonnaise stored in an airtight container in the refrigerator. Play around a little as I find it is magnificent with just about anything.