Hi BecR,
I see that noone so far has answered your request for a tried and true Streuselkuchen recipe
Unfortunately I am not fond of it myself, so I never made one, but here is the recipe from one of my two all-time favorite books on baking in my collection. Every recipe I ever made from them has turned out good and tasty. Perhaps until you find a better one you might give it a try
From: Dr. Oetker: Backen macht Freude (Das Original); 1992
Streuselkuchen (yeast dough)
For 1 rimmed baking sheet 15x13 in (or 2 10x10 in)
For dough:
13 oz flour
1 envelope dry yeast (0.25 oz)
¾ cup plus 2 tb lukewarm milk
1 ¾ oz sugar
2 oz very soft butter
2 eggs yolks
For streusel:
10 ½ oz flour
7 oz cold butter
5 ½ oz sugar
1 tb vanilla sugar (or 1 tb sugar plus 1t vanilla extract)
1 t cinnamon (optional)
For dough mix flour, yeast, sugar and salt. Add other ingredients and knead into a soft dough (5-10 minutes to develop the right texture). Let rise covered in a warm place until doubled, about 45-60 minutes.
For streusel mix all dry ingredients, add butter cut into small dice and mix (with hands or much quicker in food processor) until crumbly. Don’t overmix or you have a sort of pie dough.
Grease baking sheet. Roll out dough on sheet. Crumble streusel over dough. Let kuchen rise another 10 minutes (until it has visibly risen). Preheat oven to 400F. Bake kuchen in the middle of oven for 15-25 minutes until golden yellow.
Let kuchen cool on the sheet 10 minutes, then cut into 20 squares. Serve as soon as it is cooled.
IMO, this kuchen will dry probaply very quickly (like all yeast dough kuchen) and will be really good only fresh, fresh, fresh.
