Put the apples, water, honey, cinnamon and nutmeg into a pan and stew them slowly until they are soft and the water has evaporated. This can take about half an hour, depending on the thickness of the apples.
While the apples are stewing, get on with the custard. Pour the cream into a saucepan and heat slowly until small bubbles start to form. You don't want the cream to be anywhere near boiling, so about 60⁰ is perfect.
In a bowl, place the egg yolks and whisk in the maple syrup, collagen and vanilla extract, and then slowly whisk in the cream. It's very important to do this slowly as if you do it too quickly, the heat from the cream could scramble the eggs and you'll end up with a really lumpy custard.
To make the crumble, put all of the ingredients into an electric whizzer and blitz very slowly. You don't want to whiz it too quickly otherwise you'll form a big ball of dough. It's very important that the butter is room temperature to achieve this.
Put the apples into an ovenproof dish and pour the custard on top, then carefully spoon the crumble on top, not allowing it to clump.
Cook in the oven on 180 degrees for about 15 minutes, or until the custard starts to bubble up. Keep an eye on it and if the crumble starts to go brown then place a piece of foil over the top. Don't tuck it in at the sides, just place it on top of the crumble and that will stop it from burning