Keep a butter paper ready to place the caramelised nuts on it.
Keep your nuts ready.
Spread the sugar on a frying pan. Keep it on medium high flame. DO NOT STIR.
Let the color of the sugar change to golden brown. If there are spots where the sugar has not changed color, just swirl the pan slightly. Make sure you don't burn it.
The next steps should be done quickly. Immediately add in the nuts. Stir once and pour it on the butter paper. Try to spread it with the back of your spoon. It will be very hot, make sure you don't touch it.
Let it cool completely.
Meanwhile, add digestive biscuits in food processor and make it into a powder. Add this into a bowl and keep aside.
Once cooled, break the caramelised nuts into smaller pieces.
Place it in a food processor or grinder and pulse it until you will have nicely ground caramelised nuts. It is okay if there are few bigger pieces.
Combine this with powdered biscuits. Add in the butter and mix well.
Grease the inside of a 9" spring form pan and place a baking paper at the bottom.
Place 3/4th of the prepared crust mixture onto the bottom of the pan. Press it well. Reserve the remaining.