@piggo If you mean that strudel which "burst open", then what you did wrong is you obviously did not "air-vent" it. When you just roll it and then bake, it will almost certainly "explode" - as in your pictures. The next time take a good advice from you mom, or grandma, take a fork and *after* you smear the top with an egg yolk (the glossy top is a matter of taste of course) you poke the whole strudel roll with it. This will create holes in the pastry and when baked, the accumulated gases will have a way to vent. In result, your strudel will remain in one piece and won't explode. Good luck there!