Sift flour and sugar into a large bowl. Heat butter, cocoa and Coca-Cola to boiling point. Pour over the flour/sugar mixture and mix thoroughly. Add rest of ingredients and mix well. The batter will be thin; marshmallows will come to the top. Bake at 350F in cake pan 2 inches x 12 inches x 14 inches for 30 to 35 minutes.
Icing: Pour first 3 ingredients over confectioners sugar and mix well. Pour over cake while its is warm. Optional: add one cup toasted chopped pecans to icing first.