Preheat the oven to gas 4 / 350°F / 180C and lightly grease a 10"x 12" baking dish
Soak the dry lasagne sheets in hot water while you do the next few steps, until they're soft & pliable
Put the apples, cinnamon and vanilla in a small saucepan with the water. Put the lid on the pan, bring to the boil then let simmer uncovered for about 8 minutes until the apples are soft, the mixture has thickened and no water remains. Set aside to let cool a little
Spoon some of the custard into the bottom of the oven dish
https://cookpad.com/us/recipes/332987-vickys-vanilla-custard-gluten-dairy-egg-soy-nut-free
Lay your lasagne sheets out in front of you, sprinkle a half teaspoon of cinnamon sugar over each and divide the apple mixture evenly between them
Roll the filling up inside the lasagne sheets and place each into the dish
Pour the remaining custard over the cannellonis
Make the oat crumble topping by combining the flour, oats and butter in a small bowl and rubbing it all together through your fingers until it resembles crumbs. Then mix in the sugar and cinnamon
Sprinkle the crumble topping over and bake for 30 minutes until golden on top
Serve hot from the oven
For a 'lasagne' style layered version, spread 1/2 of the apple mixture on the bottom of the greased dish. Top with 3 pre-soaked lasagne sheets, trimmed to fit. Pour half of the custard on top. Add another layer with the remaining fruit, then the last lasagne sheets, then the custard. Sprinkle the crumble mix on top. Again, bake for about 30 minutes, until golden brown on top
