Adapted from a recipe in “Das grosse Buch vom Backen”
Filling:
1 package instant vanilla pudding, 3.5 oz.
2 cups milk
2 large egg yolks
3/4 cup sour cream
1 can blueberry pie filling
Cake:
1-3/4 cups (3-1/2 cubes) margarine, softened
1-2/3 cups sugar
1 teaspoon vanilla
1 lemon peel, grated
2 large eggs
4 cups flour
pinch salt
1 tablespoon baking powder
1/2 cup hazelnuts, finely ground (optional)
Streusel:
2-3/4 cups flour
1-2/3 cups sugar
2 teaspoons vanilla
1-1/8 cups (2 cubes plus 2 tablespoons) 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 10″ X 15″ X 2″ 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″ rim, the cake will overflow a bit in the oven. If you only have a jelly-roll pan will an 1″ rim, you can prevent overflow by lining the pan with aluminum foil, shiny side up, leaving 4″ extra all the way around. Fold the edge under, and presto! A 2″ rim! (Saves on cleanup as well.)