In a large mixing bowl stir together, 1 1/2 cups of the flour and the yeast; set aside.

In a medium saucepan heat and stir together, sugar, water, butter, 1/3 cup of the evaporated milk and salt. Heat just until warm (120 F to 130 F) and butter almost melts. Add milk mixture to flour mixture; add egg yolks. Beat with an electric mixer on low to medium speed 30 seconds, scraping the sides of the bowl constantly. Beat on high speed 3 minutes. Using a wooden spoon, stir in as much remaining flour as you can.

Turn dough out onto a lightly floured surface. Knead in enough of the remaining flour to make a moderately soft dough, that is smooth and elastic (3 to 5 minutes total.) Shape dough into a ball. Place in a lightly greased bowl, turning once to grease surface. Cover and let rise in a warm place until doubled (about 2 hours). Punch dough down. Turn dough out onto a lightly floured surface. Cover; let rest 10 minutes.

Meanwhile, in a small saucepan, combine the remaining evaporated milk, 3/4 cup of the chocolate pieces, sugar, and the 1/2 teaspoon cinnamon. Cook and stir over low heat until chocolate is melted. Remove from heat; cool.

Grease a 10-inch tube pan; set aside. Roll dough into an 18 x 10 inch rectangle. Spread chocolate mixture to within 1 inch of the edges. Starting from a long side, roll up dough. Pinch seam to seal. Place, seam side up in prepared pan. Pinch edges together.

In a small bowl combine 1/4 cup flour, 1/4 sugar, and 1 teaspoon cinnamon. Using a pastry blender, cut in 1/4 cup butter until mixture resembles coarse crumbs. Stir in remaining chocolate pieces and pecans. Sprinkle over dough in pan. Cover; let rise in a warm place until nearly double (about 1 hour). Bake in a 350 F oven about 50 minutes or until bread sounds hollow when lightly tapped. Cool in pan on wire rack for 15 minutes, remove from pan; cool for 45 minutes. Serve warm.