Combine flour, baking powder and salt in bowl. Set aside.
In food processor or blender, process cottage cheese until creamy.
Add sugar, milk, vanilla and oil to blender. Process until smooth.
Add wet ingredients to dry ingredients and stir until just combined. Dough will be slightly sticky.
Turn dough out onto floured surface and knead several times, forming into a ball. You may need to add more flour to the dough as you knead if it is too sticky. Dough should still be soft and pliable.
Refrigerate in a covered bowl for 30 minutes.
In a medium bowl, mix cream cheese and sugar until creamy.
Next add egg yolk, vanilla and lemon extract stirring until smooth.
Lay out a piece of parchment paper (approx. 13 x 17 in.).
Place chilled dough onto the parchment paper and roll it into a 12x16 in. rectangle. Try to keep the sides squared as much as possible.
Transfer the dough to a cookie sheet, removing the parchment paper and discarding it.
Spread the filling mixture down the center (lengthwise) in an approx. 4 in wide strip.
Sprinkle blueberries evenly onto filling.
On the lengthwise sides, cut 1 inch wide strips going about 4 inches in, toward the middle.
Beginning on one end, fold alternating strips into center at an angle, in a crisscross pattern.
Turn ends of pastry under.
Whip egg white and water. Brush across surface of dough.
Bake for approx. 22 minutes or until golden brown.
Cool on baking rack until warm.
Combine the powdered sugar with the lemon juice and vanilla extract, starting with 1 tbsp of lemon juice and adding more liquid as needed to achieve a drizzle consistency.