A dairy-free, egg-free shortbread base with a gooey apple filling and crumbly streusel topping.
Preheat your oven to 180°C/350°F (or 160°C/325°F if you're using a fan or convection oven).
Line an 8x10x3-inch tin with baking paper. It's important the tin is at least 3-inches deep as there is a lot to fit in there! I recommend leaving some baking paper hanging over the edges to allow for easy removal later on.
Mix together the flour and sugar in a large bowl. Rub the margarine in with your fingers, then press it together into a firm dough. If it's too sticky, add more flour and if it's too dry, add more margarine.
Press the dough evenly into the bottom of your tin. Poke small holes all over it using a fork (this will help the air to escape when baking).
Bake for 20 minutes, then set aside until you're ready to add the filling.
In a large pan or pot, mix together the water, cornflour, sugar and cinnamon. Mix while everything is cold to prevent the cornflour from becoming lumpy.
Put the sliced apples in the pan and place over medium-high heat. Cook for around 5 minutes or so, until the mixture becomes thick and syrupy and the apples have softened slightly.
Remove from the heat and set aside for now.
Mix the flour and brown sugar together in a bowl.
Rub in the margarine until you have what looks like large breadcrumbs.
Pour the apple filling over your shortbread base and spread it out evenly.
Add the crumb topping and press down into place. This will help it stick together once cut into later on.
Bake for 40 minutes.
Let the apple crumble bars sit in the tin for around 1 hour at room temperature, then transfer to the fridge for a further 4 hours. I like to leave them overnight!
Once chilled, use the baking paper to remove it from the tin. Cut into 12 square slices and enjoy!