Peel and chop the apples in small pieces, place them in a medium size saucepan, together with all the other ingredients, and make sure to add the starch and water for last. Mix well and cook on low, with a lid on, for about 10 minutes, stirring every couple of minutes.
In the meantime, prepare the pastry shell.
Preheat the oven to 350 F and cover a casserole with parchment paper.
Combine all ingredients in a food processor (or in a large bowl), and blend (or knead) until you have a nice ball of dough.
Preheat the oven to 350 F (180 C).
Roll out the dough in between two sheets of parchment paper to a 4 mm (1/8 inch) thickness and trim off any excess to give it a rectangular shape (30 x 10 cm – 11.9” x 4”).
Transfer the sheet of parchment paper that holds the rolled dough over a baking tray.
Spread the apple mixture in the middle of the dough, creating a central line of filling like you see in the photos. If you want, you can create a little motif on one of the sides cutting out little shapes with a small cookie cutter. This is optional, but it will help excess steam from the baking apples escape without affecting the strudel.
Helping yourself with the parchment paper sheet on which your strudel is sitting, fold in the short ends of the dough, and press gently on the edges to make them stick together.
Because the gluten-free pastry shell is a lot crumblier than a regular one, help yourself with the baking paper to hold the strudel tightly.
Bake for 35 to 40 minutes depending on your oven, and serve warm, ideally paired with a scoop pf dairy free vanilla ice cream!