Melt butter, sugar, evaporated milk and UHT milk in a heavy saucepan. Stir over medium low heat until butter has melted and sugar dissolved completely.
Remove pan from the heat and stir in cocoa, essence and brandy. Stir well until mixture is free from lumps.
Return pan to the heat and bring slowly to the boil stirring constantly. Reduce the heat and cook until the fudge reaches a stage whereby the mixture forms a soft ball when dropped into a bowl of cold water.
Pour the mixture into a lightly greased baking tray. Leave aside to set and cool. Mark into squares with a sharp knife.
Chill until required, then cut into squares and store in an airtight container in the refrigerator.