Break up the rice cookies in a food processor or by crushing in a bag with a rolling pin.

Put them into a bowl and mix with the powdered sugar and chia seeds

Meanwhile put the peanut butter, and vanilla into another bowl and mix in the warm melted butter till combined Stir in the crushed biscuits mixture.

Scoop into the prepared tin and push down till flat and even

Melt the butter and chocolate ( I use the microwave on short bursts) till only just warm and melted together. Spread over the peanut butter mixture till smooth and even.

Refrigerate till set

Cut into even pieces with a sharp knife