Step 1

Place butter and condensed milk into a saucepan and melt over a low heat.

Step 2

Use a rolling pin to crush the Crunchie bars, whilst they're still in their packets. Whizz up the biscuits in a food processor until they resemble a fine crumb.

Step 3

Combine the crushed biscuits and Crunchie bars in a large bowl. Add the melted condensed milk and butter mixture and mix well.

Step 4

Press the mixture firmly into a greased slice pan and refrigerate until set.

Step 5

Put the chocolate melts and oil into a glass bowl and melt it in short 30 second bursts in the microwave until smooth. Pour melted chocolate over the base and refrigerate for about 30 minutes, or until firm.

Step 6

Cut into squares and keep in an air-tight containter for up to a week.