1. Make the biscuit base first. Melt the butter in a medium-sized pan. Put the biscuits into a sealable plastic food bag and crush with a rolling pin, or pulse them until fine in a food processor. If you are crushing it yourself, don’t use too small a bag, or you’ll make a mess
2. Tip the biscuit crumbs into the melted butter and mix until they are evenly coated. Try not to leave any chunks of biscuit. Pour the mixture into the center of a 20 cm pie tin. Then press the mixture firmly over the base of the tin and up the sides. Transfer the base to the fridge to chill for about 15 minutes, until firm
5. Take the set biscuit base out of the fridge and pour the toffee onto the biscuit base. Transfer to the fridge and leave to cool completely. When it is cool, layer on the sliced bananas, if you haven’t already mixed them into the toffee
6. When it’s time to serve, pour the cream into a large bowl, and whisk with an electric hand mixer for 10-15 minutes, until thickened but not stiff. Spoon the cream over the bananas. One variation is to use plain yogurt instead of whipped cream. If you try this, the yogurt doesn’t need to be whipped