Step 1

Line a square cake tin with baking paper, allowing plenty to hang over the side. In a food processor, blitz biscuits to form a fine crumb. Add melted butter and blitz again until fully combined. Pour into the prepared tin and use a large spoon or glass to press down into an even layer. Refrigerate for 30 minutes to set.

Step 2

Place cream in a large bowl and sprinkle over instant pudding and custard powder. Use electric beaters to whip for 2 - 3 minutes until thick and smooth. Add Baileys and continue beating for a further minute.

Step 3

Pour the cream mixture over the biscuit base, smoothing the top. Refrigerate for at least 2 hours or overnight.

Step 4

Use the overhanging baking paper to lift the slice from the tin. Place on a board and sprinkle liberally with icing sugar. Slice into squares and serve.