Combine yeast and 1 1/2 cups flour in a large mixing bowl. In a saucepan,
combine sugar, water, butter, evaporated milk and salt. Heat just until warm;
add to yeast mixture. Add egg yolks.
Beat at low speed 30 seconds; beat 3 minutes at high speed. Stir in 2 1/2 cups
more flour. Place in a greased bowl; turn once to coat surface of dough. Cover;
let rise until double, about 2 hours.
Punch down; turn onto floured surface and let rest 10 minutes. Meanwhile, for
the filling, in a medium saucepan combine chocolate morsels, evaporated milk,
sugar and cinnamon. Cook and stir over low heat until chocolate melts; cool.
Roll dough to an 18-inch-by-10-inch rectangle. Spread with chocolate mixture;
roll up from long side. Seal and join ends. Place seam down in a greased 10-inch
tube pan.
For the topping, combine the flour, sugar and cinnamon. Cut in the butter; stir
in the chocolate morsels and chopped nuts. Sprinkle mixture on dough. Let rise
about 1 1/4 hours. Bake in a preheated 350-degree oven for 50 minutes. Cool 15
minutes; remove from pan.
