Preheat the oven to 180°C.
Mix butter and sugar together until well combined.
Mix in flour until it resembles breadcrumbs and spread on a baking tray.
Bake for 12 to 15 minutes until crisp and golden-brown.
Cool completely and then blend with sea salt in a food processor.
Melt the chocolate in a bowl over a saucepan of simmering water.
Beat the sea salt into the caramel condensed milk.
Whisk the whipped double cream into the caramel until stiff peaks form.
Divide the caramel mixture equally among the pastry cases.
Pour melted chocolate over each tart to coat the filling and let it harden.
Roll ice cream balls in the salted crumble mixture until coated.
Place a tart on each plate and top with a ball of crumble ice cream.