Put the sugar, butter, vinegar, and water in a really big saucepan. Over low heat while stirring occasionally, bring it slowly to a boil (about 10 minutes).
When the sugar dissolves, you can turn up the heat just a bit to let the mixture bubble for a while. Stop stirring and put a cooking thermometer in and watch until it reaches 130ºC (250ºF). This should take another 10 minutes.
Meanwhile, blend the bananas with a little cream until you have a smooth consistency. Remove any hard bits.
By now the temperature of the toffee should be 130ºC. Turn the heat off and grab a whisk and your milk. Slowly and carefully add the milk to the toffee while whisking vigorously to prevent lumps. The toffee should dissolve completely into the milk.
Leave the toffee mixture to cool.
When the mix is cool, sieve the toffee mix to remove any hard sugary bits.
Stir in the remaining cream and the bananas. You'll probably need to whisk again to remove the lumps.
That's it. Time to crank!
Triple Motion: Banoffee (Banana & Toffee) Ice Cream https://www.triplemotion.com/2008/05/04/banoffee-ice-cream/