1. Sprinkle yeast over warm milk in glass measuring cup. Stir in the 3 tablespoons flour and the 1 tablespoon sugar. Let stand until foamy, about 10 minutes.
2. Beat butter and remaining 1/4 cup sugar in bowl until creamy. Add yolks, one at a time, beating well after each. Stir in yeast mixture.
3. Combine cream and milk in small bowl. Combine 3 cups flour and salt in second bowl. On low speed, into butter mixture, beat 3 cups flour alternately with cream mixture, in 2 or 3 batches, beating well after each. With wooden spoon, stir in remaining flour; dough will be very soft.
4. Turn dough out onto lightly floured board. Knead 12 to 15 minutes or until smooth and elastic, adding more flour as needed (about 1/4 cup total) to prevent sticking. Place dough in greased large bowl, turning to coat. Cover with greased waxed paper and a clean kitchen towel. Let rise 30 minutes. Refrigerate overnight for slow rise.Prepare filling:
5. Beat eggs, sugar and cream in large bowl. Stir in walnuts. Refrigerate, covered, overnight. Remove from refrigerator 1 hour before using.
6. After dough has risen overnight, let dough stand at room temperature 2 hours. Let filling stand at room temperature for 1 hour.
7. Punch dough down. On floured work surface, divide dough in thirds. Cover 2 pieces with greased waxed paper and a kitchen towel.
8. Roll the remaining piece of dough into 18 x 14-inch rectangle. Spread with one-third of filling, leaving a 1/2-inch border all around the edge. Beginning with short side, roll up tightly, jelly-roll fashion. Place, seam side down, on greased baking sheet. Pinch ends to seal; tuck under loaf. Cover with lightly greased waxed paper and kitchen towel. Repeat with remaining pieces of dough and filling. Let rise in warm place about 1-1/4 hours* or until doubled in bulk.
9. Heat oven to 350 degrees F. Bake 45 to 50 minutes, until golden brown. Transfer to racks. Serve warm.