Finely chop the onion and sauté in oil. Add the spinach and a little water. Simmer until the spinach is soft. In the meantime, peel and press the garlic. Season to taste with salt and pepper (I also like to add a soup cube when braising, but it`s a matter of taste).
Dice the feta and the sun-dried tomatoes. Then mix the spinach, feta, tomatoes and diced potatoes in a bowl. I always let the spinach cool down a little first so that the mixture doesn`t melt right away.
Spread half of the mixture on 1 strudel dough, brush the edge with egg and roll up. Brush with egg and bake in the oven according to the package instructions.
I like to serve a sour cream-yoghurt-garlic sauce with it, but there is no limit to the imagination.