Dissolve the honey, butter and sugar in a pan over low heat. Add the granola/muesli and mix well together. Line a baking tray (20cm x 30cm ) with parchment paper and pour in the mixture. Smooth with a knife. Bake in a moderate oven (170C) until golden brown, approx 20 mins.
Remove from oven and allow to cool for about 10 minutes, then cut into slices and leave to cool completely before removing from the tin.