1. In a small saucepan, heat milk until bubbles form around edge. Remove from heat; cool to lukewarm.
2. If possible, check temperature of the warm water with a thermometer. In a large bowl, sprinkle yeast over water, stirring until dissolved. Add lukewarm milk, 1/2 cup sugar, the salt, 1/2 cup butter, the eggs, egg yolk, and 3 cups flour. With an electric mixer at medium speed, beat until smooth and blended. With a wooden spoon, stir in 1 1/2 cups flour; beat vigorously 2 minutes, or until dough leaves the side of bowl. Mix in raisins.
3. Cover with a towel; let rise in a warm place (85F), free from drafts, until double in bulk, about 1 hour.
4. Grease and flour a 9-inch springform pan. Turn the dough into the prepared pan. Cover with a towel; let rise in a warm place, free from drafts until the dough is 1/2 inch from the top of pan, about 1 hour.
5. Meanwhile, preheat oven to 350F.
6. Make the topping: beat egg white with 1 Tbsp. water; use to brush top of babka. Mix flour, sugar, cinnamon and butter; sprinkle on babka.
7. Bake 60 minutes, or until cake tester inserted in center comes out clean. Cool in pan on a wire rack 15 minutes.
8. To serve: Remove side and bottom of the springform pan. Cut into wedges. Serve warm, if desired. Makes 16 servings.