Base:
1 Packet Marie Biscuits (you can substitute with any plain sweet biscuits)
170 mg unsalted butter, melted

Filling:
400g sweetened condensed milk
Juice of 2 lemons
3 level teaspoons gelatin
1/4 cup boiling water
Topping:
1 packet jelly crystals (your choice of flavor)
Water

Crush biscuits in a food processor (or in a plastic bag with a rolling pin), transfer to a bowl and mix in melted butter. Place mixture in prepared tray and press down firmly. Refrigerate for 30 minutes.
Dissolve gelatin in 1/2 cup hot water. Combine gelatin mixture with condensed milk in a bowl, pour over biscuit base and place back in fridge for 30 minutes until cool and nearly set.
Pour cold jelly on top of biscuit crust and return to fridge to set.
Slice into squares using a butter knife.
Serve cold.