Make yeast starter: Mix scalded milk, yeast, and sugar. Let rise 10 minutes.
Make dry base: Combine flour, sugar, salt, and cut in cold butter until crumbly.
Mix wet ingredients: Whisk eggs, sour cream, vanilla. Add yeast mixture.
Form dough: Add wet mixture to dry; knead until smooth.
First rise: Place in oiled bowl, cover, and rise 2–2½ hours.
Divide: Punch down and divide dough into 4 parts.
Roll thin: Roll each piece to a 12×18-inch rectangle.
Fill: Spread with walnut, poppy seed, apricot, or prune filling.
Roll: Roll tightly from long side; place seam-side down in greased loaf pans.
Second rise: Let rise 1 hour.
Bake: Prick tops with toothpick; bake 50 minutes at 325°F.
Cool: Rest 15 minutes in pans, then cool completely on rack.
Slice and serve!