Preheat the oven to 200°C.
Biscotti crust Crush the biscotti in a food processor. Add the butter while the machine is running. Lay out in a thin layer on a baking sheet and bake for 10 minutes or until crisp and pale brown.
Apples Cut the apples into rings, about 5 mm thick. Heat the butter and oil in a pan and flash-fry over high heat. Arrange on a large baking tray.
Butterscotch sauce Slowly heat the sugar and butter, stirring until the sugar has dissolved completely. Bring to the boil and simmer until the sauce thickens. Remove from the heat and stir in the cream and liqueur. Strain through a fine sieve.
Ginger ice cream Soften the ice cream for mixing. Heat the jar of ginger in the microwave oven for 30-60 seconds or until just warm. Spoon the ginger pieces and syrup into a food processor and blend until finely ground. Fold into the ice cream and freeze until hard.
To serve Reheat the apples in the oven just before serving. Spoon a little of the crumble mix on a dessert plate or bowl. Arrange 3-5 apple slices on top and pour over a little butterscotch sauce. Top with a scoop of ginger ice cream.