Mix milk, yeast, and sugar in a standing electric mixer fitted with whisk attachment until combined well. Let stand until foamy, about 5 minutes. Add butter, eggs, salt, and 3 cups flour and beat until smooth. Fit mixer with dough-hook attachment and, with mixer on medium-high speed, gradually knead in remaining 3 1/2 cups flour, occasionally scraping down side of bowl with a rubber spatula, until dough is smooth and elastic, about 6 minutes. Transfer dough to a large oiled bowl, turning to coat, and cover with plastic wrap. Let dough rise in a warm place until almost doubled in bulk, about 1 1/2 hours. Stir together walnuts, sugars, and cinnamon. Punch down dough, then halve it. Pat each piece into a flat rectangle and cover 1 piece with plastic wrap. Roll out remaining dough on a lightly floured surface with a lightly floured rolling pin into a 17- by 13-inch rectangle (about 1/4 inch thick). Brush top with half of melted butter and sprinkle evenly with half of filling and raisins. Roll up, beginning with a short side, to form a 13-inch log and press seam to seal. Cut log crosswise into 6 pieces and arrange, cut sides up, in 2 rows of 3 buns in half of a buttered 13- by 9- by 2-inch metal baking pan. Make 6 more buns in same manner and let buns rise 30 minutes. Preheat oven to 350°F. Bake buns in middle of oven until golden brown, about 40 to 45 minutes. Beat together glaze ingredients with an electric mixer until smooth. Cool buns in pan on a rack 15 minutes, then spoon glaze evenly over warm buns.