Preheat oven to 375 degrees. Lightly grease a baking sheet, or line with parchment paper.

With an electric mixer, beat cream cheese, egg yolk and 1/4 cup powdered sugar. Stir in lemon zest and vanilla.

Remove crescent roll dough from can. Press seams together and roll into a 9x14 inch rectangle. Starting from each side of the rectangle, cut 1 inch strips into the dough, leaving the dough intact through the center.

Spoon the cream cheese mixture down the center of the dough. Sprinkle blueberries over cream cheese.

Beginning at the top of the dough, braid dough strips to cover filling, stretching slightly as needed. Tuck the last two ends under the bottom of the loaf.

In a small bowl, beat the egg white and water with a whisk. Brush over dough. Sprinkle with sparkling sugar, if desired.

Bake for about 20 minutes, or until golden brown. Cool for at least 45 minutes on baking sheet.

In a small bowl, combine remaining 1 cup powdered sugar and lemon juice. Drizzle over bread before serving.