1.Make streusel.
Process ingredients until combined. Form dough into a ball; enclose in plastic wrap. Freeze for 1 hour or until firm.
2.Preheat oven to 200°C/400°F. Grease four ¾-cup (180ml) ovenproof baking dishes.
3.Melt butter in a medium frying pan over medium hear. Add apple, sugar and 2 tablespoons water; cook, stirring, for 10 minutes or until apple is tender. Stir in marmalade. Spoon mixture into dishes.
4.Crumble streusel onto a sheet of baking paper; sprinkle over apple mixture in dishes.
5.Bake puddings for 20 minutes or until browned lightly. Serve warm with vanilla ice-cream, if you like.
The cooked apple mixture can be made a day ahead; store, covered, in the fridge.