Put the graham cracker crumbs in a bowl, then add in the melted butter and mix it all together. Spoon into the base and press against the bottom and sides. Chill it for ten minutes.
Make the caramel:
Melt the butter, salt, and dark brown sugar into a non-stick pan over low heat, stirring continuously until the sugar has dissolved.
Add the condensed milk and bring to a rapid boil for about a minute, stirring the whole until it forms a thick golden caramel.
Spread the caramel over the cooled base, let cool, and then chill for about 1 hour, until firm or you're ready to serve.
For the topping:
Toss the banana slices with 1-2 teaspoons of lemon juice to stop them from browning. Set aside.
Add powdered sugar (to taste), skimmed milk powder, and vanilla extract to the heavy whipping cream.
Using a food processor, whip the cream until it thickens (this doesn't take long at all so check often). When you run a spoon through it, and it holds its shape without falling back into the gap, it's ready to use.
Place the banana slices over the caramel layer in the base.
Cover the banana slices with the whipped cream.
Decorate with grated chocolate and banana chips and serve.