Danish Kringle

In a large bowl, cut 1 cup butter into flour until crumbly, leaving pea-sized chunks.
Stir in sour cream, and mix well; the dough will be very sticky.
Form the dough into a ball.
Cover tightly and refrigerate for 8 hours, or overnight.
Preheat the oven to 375 degrees F (190 degrees C).
Lightly grease a baking sheet.
Prepare the filling by combining 1 cup butter, brown sugar, and 1 cup chopped walnuts.
Divide the dough into three equal parts; return two parts to the refrigerator to keep cold.
Quickly form 1/3 of the dough into a rectangle and flour lightly.
On a heavily floured surface, roll out to approximately 12x17 inches.
Position lengthwise on the work surface.
Along the long edges of the dough rectangle, use a sharp knife to cut 4-inch long angled lines about 1/2 inch apart.
Spoon 1/3 of the filling along the length of the rectangle's uncut center.
Alternating from one side of the dough to the other, fold each 1/2 inch wide strip towards the center, crisscrossing the filling in a braid-like fashion.
Lightly press together the ends of the strips to seal.
Sprinkle with 1/3 of the remaining walnuts.
Repeat with remaining ingredients to form 3 braided danishes.
Arrange danishes on a prepared baking sheet.
Bake for 30 minutes in the preheated oven, or until golden brown.
Cool for approximately 30 minutes.
While the danishes are cooling, prepare the icing: mix confectioners sugar and water until smooth.
Drizzle in fine streams over warm danishes.