In a large mixing bowl stir together 1 cup of the flour and the yeast. In a medium saucepan heat and stir sour cream, the 1/4 cup sugar, the water, butter or margarine, and salt just until warm (120 degrees F. to 130 degrees F.) and butter almost melts. Add sour cream mixture to flour mixture along with the egg. Beat with electric mixer on low to medium speed 30 seconds, scraping bowl constantly. Beat on high speed for 3 minutes. Using a wooden spoon, stir in as much of the remaining flour as you can.

Turn dough out onto a lightly floured surface. Knead in enough of the remaining flour to make a moderately soft dough that is smooth and elastic (3 to 5 minutes total). Shape dough into a ball. Place dough in a lightly greased bowl; turn once. Cover and let rise in a warm place until double in size (about 1 hour).

Punch dough down. Turn out onto a lightly floured surface; cover and let rest for 10 minutes. Meanwhile, for filling, in a small mixing bowl stir together cream cheese, the 1/3 cup sugar, and vanilla; set aside. Lightly grease a baking sheet; set aside.

On a lightly floured surface, roll dough into a 14x10-inch rectangle. Spread filling evenly over dough to within 1/2 inch of edges. Roll up, jelly-roll style, starting from a long side. Seal seam. Place, seam side down, on prepared baking sheet. Make 1/4-inch-deep cuts across top of loaf at 2-inch intervals. Cover; let rise in warm place for 30 minutes. Bake in a 350 degree F. oven for 30 to 35 minutes or until golden. If necessary, cover with foil the last 15 minutes of baking to prevent overbrowning. Cool slightly on a wire rack. Drizzle with Powdered Sugar Icing. Serve warm with fresh fruit, if desired. Makes 10 servings.

In a bowl mix 1 cup sifted powdered sugar, 1 tablespoon milk, and 1/4 teaspoon vanilla. Stir in additional milk, 1 teaspoon at a time, until the icing is easy to drizzle.

Mix and knead dough as above. Shape dough into a ball. Place in a lightly greased bowl; turn once. Cover and chill dough in the refrigerator for 24 hours. Remove from refrigerator and let stand, covered, at room temperature for 20 minutes. Punch dough down. Continue as directed above.