Sprinkle yeast on warm water; stir to dissolve. Blend in egg, 3 cups of flour, cardamom, sugar and salt. Beat with mixer at medium speed about 2 minutes til batter is smooth. Add butter and enough remaining flour, a little at a time, first with spoon and then by hand, to make a fairly soft dough that leaves the sides fo the bowl. Turn onto lightly floured board. Knead til smooth and elastic ( 8 minutes). Place in greased bowl and turn over to grease top. Cover and let rise in warm place until doubled, about 1 hour. Punch down dough, turn over and let rest 10 minutes. Turn out onto board; divide dough in half. Shape into 2 loaves and place in greased loaf pans. Cover, let rise til doubled; bake at 400 degrees for 40 to 50 minutes, covering with foil during last 15 minutes to prevent browning too much. Remove from pans and cool on racks.