Into large bowl, measure sugar, butter, eggs, cinnamon, and 2 cups flour. With mixer at low speed, beat ingredients until well mixed, constantly scraping bowl with spatula. Increase speed to medium, beat mixture 3 minutes or until very light and fluffy, occasionally scraping bowl. With spoon, stir in remaining flour to make a soft dough.

Preheat oven to 375 degrees. With damp cloth, moisten 1 large cookie sheet. Spread 1/3 cup dough in a very thin layer onto each circle. Bake 8-12 minutes until lightly browned around the edges. Cool 5 minutes. Carefully remove cookies still on waxed paper to cool. Allow cookie sheets to cool before using again. Stack cookies, cover with plastic wrap and store in cool, dry place.

EARLY IN DAY OR DAY AHEAD: Coarsely grate chocolate squares, set aside. Beat cream and cocoa until soft peaks form. Spread cookies with 1/2 cup whipped mixture and layer; may add nuts and chocolate, ending with whipped cream on top. Pile grated chocolate on top, refrigerate until serving time, at least 3 hours, so cookies soften for easier cutting. 14 servings.