Before you start, preheat oven to 200°C. Set aside a small baking dish (about 20cm x 15cm).
Prep apples. Pull out stems from apples and stand upright and cut in half horizontally. Use a spoon to scoop out any seeds. Place apples (skin side down) in dish and bake for 10 minutes.
Prep crumble. Place oats, brown sugar, flour, cinnamon and nuts in a bowl and pour in melted butter. Mix, until just combined and resembles a crumble.
Cook crumble. After initial 10 minutes cook time, remove apples from oven and top with crumble. Bake on middle rack of oven for 20-25 minutes, until apples are soft and crumble is golden. Reduce temperature if crumb starts to brown too quickly.
Make caramel sauce. While apples bake, place second measure of butter, sugar and salt into pot on a low heat. Whisk continuously, until sugar has dissolved and is no longer separate from the butter. Add milk/cream slowly, until sauce reaches desired consistency (it will thicken as it cools).
Serve apple halves topped with a scoop of ice cream or dollop of cream and drizzle with salted caramel sauce.