1. If making in an ice cream machine, put half of the jar of banana toffee into the compartment, add the custard and cream, quickly fold together then churn until the mixture is on the point of freezing (that is very thick) this should take about 20-25 minutes.
2. Turn into a shallow freezer proof container, add the rest of the banana toffee in blobs and then swirl through the icecream. Cover and freeze.
3. If making the ice cream without an ice cream machine, lightly whip the cream until it thickens, do not over whisk. Fold in the custard and half of the banana toffee. Turn into a freezer proof container and freeze until the mixture starts to freeze around the edges. Take out of the freezer, turn into a bowl and beat until smooth again. Return to the freezer proof container and freeze for another hour.
4. Remove from the freezer and give the icecream another mix. Return to the freezer proof container and swirl in the remaining banana toffee. Cover and freeze until firm. This method should take about 4 hours.