1. Sprinkle yeast and 1/2 teaspoon of the sugar over very warm water in a 1 cup measure. Stir to dissolve; let stand until bubbly about 10 minutes.
2. Heat milk, butter, remaining sugar and salt in small saucepan just until butter is melted. Pour into large bowl; cool to lukewarm.
3. Add eggs and yeast to cooled milk mixture; beat until blended. Add 11/2 c flour mixed with cardamom; beat 2 minutes. Stir in just enough remaining flour to make a soft dough. 4. Turn out onto lightly floured surface. Knead until smooth and elastic, about 8 minutes. Place dough in medium size greased bowl, turning to bring greased side up. Cover; let rise in a warm place, away from drafts, 11/2 hours or until doubled in volume. Punch dough down; let rest 5 minutes.
5. Divide dough in half; roll to make 2 12x9 inch rectangles. Spread each rectangle with 2 tablespoons soft butter.
6. Combine brown sugar, cinnamon, raisins and walnuts in a small bowl; sprinkle half the mixture over each dough rectangle. Roll up each tightly jelly roll fashion, from long side, pinching seam to seal well.
7. Place each seam side down on greased cookie sheet and shape into a circle; pinch ends well to seal.
8. Make cuts 2/3 of the way from outside edge through to the dough and 1 inch apart with scissors or sharp knife. Turn each section, cut side up, so filling shows. Cover; let rise until doubled in volume, about 45 minutes.
9. Bake in 375º oven for 25 minutes or until golden brown and ring sounds hollow when tapped. Cool. Drizzle with sugar Icing