Step 1

Line a square cake tin with baking paper, allowing plenty to hang over the side to make it easy to lift out the finished slice. Arrange Lattice biscuits upside down in the base of the tin.

Step 2

Place milk and cream in the bowl of a stand mixer with the whisk attachment. Sprinkle over instant pudding and custard powder. Beat for a minute until well combined, then add orange zest and juice, and continue beating for 4 minutes until thick.

Step 3

Spread custard mixture over Lattice biscuits in tin and smooth out evenly. Top with remaining Lattice biscuits. Refrigerate for at least an hour or overnight.

Step 4

To make the icing, sift icing sugar into a bowl. Add orange juice and mix into a smooth icing.

Step 5

Using overhanging baking paper, remove slice from the tin and place on a serving plate. Drizzle over icing, slice into squares and serve.