The restaurant was renown for its yeasted coffeee cake. The cake, known in Germany as Streuselkuchen, is a German specialty, a yeast dough covered with a sweet crumb topping called streusel. The streusel is key for the Heinemann cake.
Here is the Streuselkuchen recipe by Patricia_Scarpin at KeyIngredient.com at https://www.keyingredient.com/recipes/89634/streuselkuchen-german-crumb-cake/
German Yeast Dough Ingredients:
1 c. milk
2 1/4 t. yeast
1/4 c. + 1 t. sugar
1/2 c. butter, melted
1 t. lemon zest
5 c. flour
Struesel (Crumb Topping) Ingredients:
1 c. flour
1/2 c. confectioner’s sugar
1/2 c. salted butter, cold
2 t. vanilla
Directions for German Yeast Dough:
Scald milk in a small saucepan. Remove pan from heat and let stand until the milk is warm, about 10 min.; 110 to 120ºF.
Sprinkle the yeast and 1 t. of sugar into the milk and stir well. Let stand for about 10 min., until the yeast is bubbly and foamy.
Make the dough using a stand mixer: combine 2-1/4 c. of the flour with the remaining sugar in the bowl of the mixer and add the butter and lemon zest. Attach the flat beater and mix on low speed for about 3 min. Add the remaining flour 1/2 c. at a time until the flour looks mealy. Remove the bowl from the mixer stand, add the yeast and eggs, and stir with a rubber spatula to make a moist, thick dough. With dough hook, beat on low speed 1 min. Increase the speed to medium and beat 5 min., or until the dough becomes sticky and elastic and begins to pull away from the sides of the bowl.
Sprinkle 1 T. flour over the dough and cover tightly with plastic wrap. Let the dough rise until doubled in size, 1 hour or more.
Lightly flour a work surface. Dislodge the dough onto the work surface and turn to coat all surfaces lightly with flour. Divide in half. Shape each half into a ball, cover loosely with a clean kitchen towel and let rest for 10 min. The dough is now ready to use.
Directions for Streuselkuchen:
Butter a 9” square baking pan. Roll the dough on a lightly floured surface to the size of the pan. It will be about ¼” thick. Transfer the dough to the pan and pat it onto the bottom and into the corners. Do not make a rim; the dough should be flat. Cover with a kitchen towel.
Make the Streusel Crumb Topping:
Put the flour, confectioners’ sugar, vanilla and butter into the work bowl of a food processor or mixer . let the machine run just until the ingredients begin to form small crumbly masses. Do not process beyond the crumb stage.
Uncover the dough. Press the crumbs to form clumps the size of large peas, and sprinkle on the top of the dough. Continue making larger lumps of streusel and sprinkling them evenly all over the dough. There will be a generous layer of streusel covering the dough. Cover the Streuselkuchen with a kitchen towel and let stand at room temperature for 20 min.
Adjust an oven rack to the center position and preheat to 350ºF.
Uncover the kuchen and place the pan in the oven. Bake for about 30 min., until the kuchen has risen almost to the top of the pan and is golden brown and a toothpick inserted into its center comes out clean. Remove the pan from the oven and immediately sprinkle the top with a generous layer of vanilla confectioners’ sugar. Cool completely on a wire rack. This is at its best when very fresh. Cut into portions with a sharp knife.