Preheat your oven to 350 F (180 C)
In a small skillet melt the butter. Cook over a medium heat until it foams up and smells nutty. Pour 2 tbsp of the browned butter into a bowl and set aside.
Add the sugar, milk and salt to the skillet and stir in. Heat on medium until it starts to bubble, reduce to a low heat and leave to caramelise. Meanwhile cut the apple into slices, and the slices in half. Once the caramel has been cooking for about 3 minutes stir in the vanilla, then add the sliced apple and coconut. Leave to cook on a low heat whilst you make the topping.
Add the flour, sugar, oats and cinnamon to the browned butter in the bowl. Use your fingers to rub the butter into the dry ingredients. Scatter this mixture over the appley caramel mixture, remove from the heat and put straight into the oven for 15 minutes.