Step 1

Place boiling water in a small bowl and sprinkle over gelatine. Leave for a minute to soften, then whisk in with a fork until completely dissolved. Place custard in a large bowl. Add gelatine mixture and whisk to combine.

Step 2

Line a 20cm square cake tin with baking paper, allowing some to overhang. Arrange Lattice biscuits upside down in the base. Pour over custard, then arrange the remaining biscuits on top, right side up. You may need to cut some biscuits to make it fit.

Step 3

Refrigerate for 2 hours to set the custard.

Step 4

To make icing, sift icing sugar into a bowl. Mix in passionfruit pulp and margarine to form a smooth icing. Add a little milk if it’s too thick. Use overhanging baking paper to carefully lift slice out of tin. Drizzle icing over slice, then cut into squares and serve.