Step 1

Grease a 3cm-deep, 18cm x 28cm slice pan. Line base and sides with baking paper, extending paper 5cm above edges on all sides. Place biscuits in a food processor. Process until fine crumbs. Add butter. Process until just combined. Press biscuit mixture into base of prepared pan. Refrigerate for 15 minutes or until firm.

Step 2

Meanwhile, make Lemon filling: Place 1 1/2 tablespoons boiling water in a small bowl. Sprinkle over gelatine. Stir until gelatine dissolves. Wipe food processor clean. Add cream cheese. Process until almost smooth. Add condensed milk, lemon rind and juice. Process until combined. Add gelatine mixture. Process until combined. Pour over prepared base. Level top. Using a knife, score a criss-cross pattern in top of mixture. Refrigerate for 2 hours or until set.

Step 3

Make Marshmallow topping: Place 1/2 cup boiling water in a small bowl. Sprinkle over gelatine. Stir until dissolved. Place sugar and 2 tablespoons water in large bowl of electric mixer. Beat on high speed for 4 minutes. With motor operating on medium speed, slowly pour in gelatine mixture. Beat on high speed for 7 minutes or until thick and fluffy. Beat in vanilla. Spread marshmallow over filling. Refrigerate for 2 hours or until firm. Serve slice cut into squares.