Sift flour on a flat surface and make a well in the middle of it.
Add sugar, salt and egg yolk into the well. Cut butter into small pieces and add into the well.
Cut all with a knife first and then knead quickly with cool hands to form a dough. Cover dough and place in the fridge for at least for 20 minutes (you can keep it in the fridge for several hours or overnight).
Meanwhile grease a 9-10 inch spring form.
Soak raisins in small bowl with dark rum (can be replaced by water).
Sprinkle work top lightly with flour. Roll out dough large enough to cover bottom and sides of spring form. Line form with dough. Prick dough several times with a fork. Cover and place pan in the fridge.
Preheat oven (320 F, 160 C).
Meanwhile prepare the filling: Take raisins from rum (or water) and drain on paper towels.
Put curd in a clean kitchen towel, gather 4 corners and wring as much whey as possible out of the curd. It has to be as dry as possible. Save the whey. Weigh dry curd. You will need 1 2/3 pounds of dried curd for the recipe.
Measure whey. Fill up with low fat milk to 1 cup (if necessary).
Mix vanilla pudding mix with 2/3 of the sugar and milk.
Bring whey to a boil. Remove from heat. Add vanilla pudding mixture and stir. Boil up for a few times.
Remove from heat again. Under perpetual stirring add curd and vanilla extract. Bring to a boil for a last time. Put mixture in bowl and add raisins.
Beat egg white until stiff. Add remaining sugar. Fold stiff egg white under the curd mixture.
Take dough out of the fridge and add curd filling and flatten.
For brushing mix egg yolk with milk and spread carefully over the filling after 30 min of baking time.
Bake Käsekuchen in the middle of the oven for about 45-60 minutes.
IMPORTANT NOTES : Baking time depends on the moisture of the filling. If cake gets too brown, cover it with baking paper and reduce heat. Cake should not rise much. If necessary reduce heat. Cake is done, when toothpick comes out dry with no filling attach to it.
When cake is done remove from oven and detach side of the cake immediately from pan, but leave in pan for another 10 minutes. Open spring form pan and let cake cool completely.
NOTE: Curd is a German speciality with a fat content of 10 % in dry mass. You can replace it by low fat ricotta or low fat cottage cheese. If you replace curd by ricotta or cottage cheese use low fat milk instead of whey.
Or you can make German Quark (German Quark) to make it a typical German Cheesecake.