Start by making the chutney. Blend together all the ingredients with 4 tbsps water, adding only one chilli to start with as the heat varies a lot from one batch to the next. Blend until very smooth and creamy; it might take a few minutes. Taste and adjust seasoning. Keep in a glass jar in the fridge or freeze until ready to use.
Spread the butter on one side of each slice of bread and turn over.
Spread 1 tbsp of the tangy coriander chutney on 4 of the slices of bread. Spread the mayo on the other four slices.
Arrange the tomatoes evenly over the top, and the cheese and then finish with the other slice of bread, butter side up.
Place in a toasty maker and cook until golden. If you don't have a toasty maker, fry in a hot pan on both sides until crispy.