Filled Streusel Cake (Gefuellter Streuselkuchen)
Rec.food.recipes/Jeffery D. Snarr (1999)
Adapted from a recipe in Das grosse Buch vom Backen

Filling:
1 (3 1/2 oz) package instant vanilla pudding
2 cup milk
2 large egg yolks
3/4 cup sour cream

1 can blueberry pie filling

Cake:
1 3/4 cup (3 1/2 cubes) margarine, softened
1 2/3 cup sugar
1 tsp. vanilla
1 lemon peel, grated
2 large eggs
4 cups flour
pinch salt
1 Tbsp. baking powder
1/2 cup hazelnuts, finely ground (optional)

Streusel:
2 3/4 cup flour
1 2/3 cup sugar
2 tsp. vanilla
1 1/8 cup (2 cubes plus 2 Tbsp.) margarine, chilled

Preheat oven to 400 F.

Make the filling: Prepare pudding according to package directions. Add egg yolks and sour cream and blend well. Place in refrigerator until ready to use.

For the cake, cream margarine, sugar, and vanilla. Stir in lemon peel and eggs. Sift flour salt, and baking powder into a separate bowl. Add hazelnuts, if using, and stir well. Add flour/nut mixture by spoonfuls to sugar mixture.

Grease a 10x15x2-inch pan well.* Press dough (should be fairly stiff) evenly into pan. Spread pudding mixture evenly on top of dough, then blueberries on top of that. For the Streusel, put remaining flour, sugar, and vanilla in a bowl. Chop well-chilled margarine into small chunks and sprinkle into the bowl. With both hands, rub mixture until crumbly chunks (Streusel) form. Sprinkle over blueberries. Bake on middle oven rack for 45-50 minutes, until Streusel are golden brown.

*If your pan does not have a 2-inch rim, the cake will overflow a bit in the oven. If you only have a jelly-roll pan will an 1-inch rim, you can prevent overflow by lining the pan with aluminum foil, shiny side up, leaving 4-inch extra all the way around. Fold the edge under, and presto! A 2-inch rim! (Saves on cleanup as well.)