Here's a no-bake slice that's easy to make with pantry staples.
250g (8 oz) Digestive or plain biscuits
100g (3½ oz) butter
125g (4½ oz) caster (superfine granulated) sugar
2 Tbsp cocoa powder
1 medium (size 6) free-range egg
½ cup walnuts, chopped
1 Crush biscuits in a bowl with the end of a rolling pin.
2 Put butter and sugar in a saucepan and heat gently over a low heat, stirring for 2 minutes. Stir in cocoa and cook for 1 minute. Remove pan from heat and stir in egg, then biscuits and walnuts.
3 Turn mixture into a shallow tin approximately 25cm x 18cm, (9-10” x 7”, or similar) lined with baking (parchment) paper. Press smooth with your fingers. If liked, mark a pattern on the top with the tines of a fork (kids love doing this). Cool for 10 minutes, then cut into squares, but leave to cool completely in the tin. Transfer to a container and store airtight. It will keep for about a week.