Whisk the cream with the vanilla until just starting to stiffen. In a separate bowl, beat the peanut butter with the icing sugar to slacken, then fold the peanut butter mixture and the crushed banana chips into the cream. Tip into a container and chill in the fridge for a few hours or overnight.
To serve, paint a stripe of salted caramel sauce over two large plates, then scatter the stripe with the crushed brittle.
Using a dessert spoon, scoop the parfait into an oval shape (a quenelle) and sit it on one side of the plate. Top the parfait with a standing row of three banana chips, then serve.