Take chocolate and butter in a microwave safe bowl and microwave for 15 seconds. Remove and stir well. Again microwave for 15 seconds. Remove and mix. At this stage, chocolate would start melting.
Microwave for another 10 seconds and stir well. If chocolates is melted then you go ahead with the process, if not then again put it in the microwave for another 10 seconds.
Add condensed milk in the melted chocolate and give a nice stir. Add crushed biscuits and nuts and mix well everything.
Shift the mixture to a greased pan or silicon moulds and refrigerate for 1-2 hours.
My Tip: 1. If you are using some lightly sweet biscuits then use some powdered sugar to adjust the sweetness.
2. Any nuts of your choice can be used.