Butter a rectangular tin ready. Melt butter in large saucepan over low heat.

Add marshmallows and stir until melted and well blended. Cook 2 minutes longer, stirring constantly. Remove from heat. Add cereal. Stir until well coated.

Using grease proof paper, press mixture evenly and firmly into the buttered rectangular tin. Cut into rectangular bars when cool.

When the bars have cooled down, melt the white chocolate in a bowl over a saucepan. Once the chocolate is melted take the cut up krispie bars and dip the bottom of each bar in the melted white chocolate and leave to set.