Place the biscuits in the bowl of a food processor and pulse until they resemble breadcrumbs. Add butter and process to combine. Firmly press over base and halfway up sides of a greased 20cm loose-bottomed tart tin. Bake at 180C for 8 minutes. Remove and stand on the bench.
Heat the gelatine in ¼ cup water in a saucepan filled with until dissolved. Keep warm. Combine the milk, vanilla, Natvia and peanut butter in the bowl of a food processor. Process until combined. Pour in in the gelatine and combine. Pour mixture onto biscuit base. Cover and refrigerate for 2-3 hours or until set.
Slice bananas and decorate the the pie with them. Dollop or pipe cream around the banana