Heat the milk and water with a teaspoon of sugar and a pinch of salt in a large saucepan and cook the corn on the cob over medium heat for about 20 minutes. Remove from the milk and drain well. Scrape off the peel of the limes with a kitchen grater. Chop the chilli peppers too. Mix the lime zest and chilli pepper well with the soft butter and season with a little salt. Grill the corn on the cob in a grill pan with hot olive oil for about 5-8 minutes and serve with the lime butter.