Take very ripe bananas, peel them, cut them in coins (you should be left with 400-450gr), toss them with the demerara sugar and the sea salt and bake in the oven at 175C for 25-30min until the syrup thickens and the bananas are very fragrant. Remove from the oven, cool 5min, transfer the bananas along with syrup into a blender, add the cinnamon powder, the vanilla bean extract and the rum and whizz away until super smooth.
Dissolve the cornstarch in 50ml whole milk, leave to rest.
In a small saucepan bring the leftover whole milk to an almost boil, add the cornstarch milk and cook constantly stirring until thickened. Take off heat, cool 5min then add the mixture to the banana purée and blend again until fully mixed. Cool to room temperature and transfer into the fridge overnight.
Freeze in your ice cream maker according to the manufacturer's instructions adding the chocolate shreds and the chopped chocolate chip banana bread crumbs (preferably homemade or very good quality store-bought) at the last couple of minutes of churning. Store in an airtight container in the freezer for at least 4 hours until set or spoon right away.