Add the wai (water) in to a small bowl. Add the paura tetepe (gelatine powder) and stir with a fork until combined. Leave to bloom for 5 minutes.
Add the tiakarete mā (white chocolate) and ⅓ C kirīmi (cream) in to a medium, heat proof bowl. Place it over a pot of barely simmering water (about 3 cm deep) and gently melt. Make sure the bowl doesn't touch the water. Remove from the heat and leave to the side to cool. Turn the heat off the pot of simmering water and place the ranunga tetepe (gelatine mixture) bowl in to the water to gently melt it. As an alternative, melt it in the microwave for 20 seconds.
Leave for 2 minutes to cool. Then, in two additions, stir the melted gelatine mixture in to the tiakarete mā (white chocolate). Leave aside. Add the room temperature kirīmi tīhi (cream cheese) in to a large bowl. Whisk it with electric beaters for one minute until smooth.
Add the puehu huka (icing sugar), kiri rēmana (lemon zest), wai rēmana (lemon juice) and wanira (vanilla) in to the kirīmi tīhi (cream cheese).Tāwhiuwhiua - whip it, on low speed for a minute until smooth. Add a third of the white chocolate mixture at a time. Whip on low speed (for around 15-20 seconds) after each addition, until smooth.
To a medium bowl add the kirīmi (cream). Whip until it starts to thicken. Add the kirīmi kawa (sour cream) and continue to whip until thick.
Fold the ranunga kirīmi (cream mixture) in to the cream cheese mixture in two parts, folding after each addition.
Pour it on top of the paparanga pihikete (biscuit layer) and smooth it out.
Refrigerate for 5 hours. I prefer to leave it overnight to develop in flavour. This will last in the fridge for up to five days. If you are making it ahead, cover it with a plate or bowl cover.