Pyrizhky (Baked Turnovers)

Yield:	10 Servings
Categories:	Russian, Christmas, Desserts

2 1/2	c	Unbleached All-Purpose Flour
1/4	lb	Butter; 1 Stick
1/2	c	Sour Cream
3	lg	Egg Yolks
1/2	ts	Salt
1	lg	Egg White; Beaten With A Little Water For Glazing
1/2	c	Coarse Sugar Crystals; (Optional)