Combine sour cream, sugar, butter, and salt; mix well and let cool to lukewarm. Dissolve yeast in warm water (105-115 degrees) in a large mixing bowl. Stir in sour cream mixture, then eggs.Gradually stir in flour (dough will be soft). Cover tightly and chill overnight. Dough can be refrigerated for up to 4 days before being used.
Divide dough into fourths. Turn each portion out on a heavily floured surface and knead 4 or 5 times. Roll each into a 12x8 rectangle. Spread 1/4 filling over each rectangle, leaving a 1/2 inch margin.
Roll up jelly roll fashion, beginning at long side. Pinch each edge and ends. Place on greased baking sheets.
Make 6 X-cuts across the top. Cover and let rise in warm place about an hour. Bake at 350 for 15-20 minutes. If edges get too brown before rest of braid, tent ends with foil.
To make glaze, combine powdered sugar, vanilla, and half and half and mix until completely combined. Glaze should be thick. Place glaze into quart-sized plastic bag and cut a small hole in one corner. Pipe glaze over warm braids.