In large bowl, combine 1 cup flour, yeast, sugar and salt.

Heat milk, water and butter until liquids are very warm (120º to 130ºF). Gradually add to dry ingredients; beat 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add eggs and 1/2 cup flour; beat at high speed 2 minutes, scraping bowl occasionally. Stir in enough remaining flour to make soft dough.

Knead on lightly floured surface 4 minutes or until smooth and elastic. Place in bowl coated with cooking spray. Spray top of dough with cooking spray. Cover; let rise in warm, draft-free place until doubled in size, about 1 hour. (For Fleischmanns® Rapid Rise Yeast, cover kneaded dough. Let rest on floured surface 10 minutes. Proceed with recipe.)

Roll dough to 18- × 12-inches. Spread Walnut Filling on rectangle to within 1-inch of edges. Roll up from long side as for jellyroll. Pinch seam to seal. Fold roll in half, bringing one end on top of other end. Pinch ends to seal and tuck under. Place on baking sheet coated with cooking spray. Measure to locate center. Starting 1 inch from center, cut to each end (leave 2 inches uncut in center). Lift, pull and spread out wings of butterfly, laying open each section with cut side up. Cover; let rise in warm, draft-free place until almost doubled in size, about 45 minutes.

Bake at 350ºF for 25 minutes or until done. Cool on wire rack. Top with Confectioners Sugar Frosting. ____________________ To Make Walnut Filling: In medium bowl, combine all ingredients. To Make Confectioners Sugar Frosting: Combine 1 cup confectioners sugar with 4 to 5 teaspoons milk and 1/2 teaspoon vanilla extract. Beat until smooth.