Line large baking sheet with parchment paper.
In food processor, combine flour, sugar, butter, & salt. Pour mixture into large mixing bowl & add in one egg yolk. Knead with your hands until smooth.
Let sit in refrigerator for 1.5 hours.
Preheat oven to 360 F. Mix in extra egg yolk to dough. Add water in increments of 1 tablespoon as needed to help dough stick together. Place dough on large cutting board & roll out until about 1.5 cm in height.
Cut dough into even number of tiny rectangles. Place half of the rectangles on parchment paper & place 1 tsp of cookie dough directly in center of dough.
Lightly brush the edges of filled dough with water. Place evenly sized dough on top of filled dough & press down on sides to close. Press the edges of the dough with a fork to secure rectangles together.
Bake for 20-30 minutes until golden brown. Let cool & begin making icing by combining all ingredients at once in bowl. Combine all glaze ingredients & top immediately.