For the Strudelschüsserl with chestnuts, potatoes and grapes, first peel the potatoes and cut them into small pieces, boil them in plenty of salted water until soft, drain them and let them steam out.
Cut the grapes in half, chop the chestnuts coarsely and stir both into the potatoes together with the rosemary and the egg. Season the mixture with salt, pepper and nutmeg.
Lay out a layer of strudel dough on a tea towel and brush with butter, place a second layer of strudel dough on top and brush again, repeat until all the strudel dough sheets are used up.
Cut 10 x 10 cm squares from the strudel dough, place the strudel dough in a muffin tin and fill with the potato mixture. Brush the overlapping ends with butter, bake the strudel bowls at 200 °C convection oven for about 25 minutes.
Remove the strudel bowls with chestnuts, potatoes and grapes from the oven and allow to cool slightly, then serve immediately.