In large mixer bowl combine 1 1/2 cups all-purpose flour and 2 packages active dry yeast. Heat 3/4 cup sugar, 2/3 cup water, 1/2 cup butter, 1/3 cup evaporated milk and 1/2 teaspoon salt just until warm (115 to 120 degrees), stirring constantly to melt butter. Add to dry mixture in mixer bowl. Add 4 egg yolks. Beat at low speed with electric mixer for 1/2 minute, scraping bowl. Beat 3 minutes at high speed. By hand, stir in 2 1/2 cups all-purpose flour to make a moderately soft dough. Place in greased bowl, turning once. Cover; let rise until doubled, about 2 hours.

Punch down; turn out on floured surface. Cover; let rest 10 minutes. Meanwhile, combine 3/4 cup semi-sweet chocolate pieces, 1/3 cup evaporated milk, 2 tablespoons sugar and 1/2 teaspoon ground cinnamon. Stir over low heat until chocolate melts; cool. Roll dough to 18"x10" rectangle. Spread with chocolate mixture; roll up from long side. Join ends. Place in greased 10" tube pan.

Combine 1/4 cup all-purpose flour, 1/4 cup sugar and 1 teaspoon ground cinnamon. Cut in 1/4 cup butter; stir in 1/4 cup semi-sweet chocolate pieces and 1/4 cup chopped nuts. Sprinkle on dough. Let rise until double (about 1 1/4 hours). Bake at 350 degrees for 45 to 50 minutes. Cool 15 minutes; remove from pan. Makes 1 coffee cake.