Make the chipotle butter: Soak the dried chillies in hot water for ten minutes, then drain and chop finely. Mash them into the softened butter with the chopped coriander and a little seasoning. Set aside.
Char the corn: If using cobs, slice off the kernels. Heat the oil in a heavy frying pan until very hot, add the corn in a single layer and leave it to char for 3 to 4 minutes before stirring, until blackened in spots.
Steam it through: Add a splash of water to the pan and cook for a few minutes more until the water evaporates and the corn is tender. Tip into a bowl to cool slightly.
Melt the butter through: While the corn is still warm, stir the chipotle butter through it so it melts and coats every kernel.
Mix the dip: Fold in the soured cream, mayonnaise, most of the cheese, the garlic, lime zest and juice, and the spring onions. Season, then taste for lime and heat.
Serve: Spoon into a bowl, scatter with the rest of the cheese, extra coriander and chilli, and serve warm with tortilla chips.
