Stir the tahini to loosen, then mix with the syrup, vanilla and 120ml hot water in a heatproof bowl. Sift in the cocoa and espresso, if using. Stir in a pinch of salt until smooth, adding a splash more hot water to loosen, if needed.

Put the banana chunks on a tray. Freeze for 1 hr, then blitz in a food processor until smooth with enough milk to create a creamy texture. Will keep frozen for three months.

Top the banana ice cream with the tahini sauce and banana slices. Extra sauce will keep in an airtight container at room temp for four days.