Preheat oven to 350 degrees F (175 degrees C). Grease one 9×13 inch cake pan.
In a small saucepan, combine 1/2 cup butter, 1/2 cup shortening, 2 ounces chocolate, and water. Heat until chocolate is melted; set aside.
In a large bowl, combine flour, sugar, cinnamon, and baking soda. Make a well in the center, and pour in buttermilk, eggs, and vanilla. Add melted butter/chocolate mixture, and beat until smooth. Pour batter into prepared pan.
Bake in preheated oven for 20 to 25 minutes, or until cake tests done. Five minutes before cake is done, make frosting.
To make frosting: In a saucepan, combine 1/2 cup butter, 2 ounces chocolate, and 6 tablespoons milk. Heat until bubbles form around the edge; remove from heat.Beat in confectioners’ sugar, 1 teaspoon vanilla, and nuts. Frost cake while still warm. Allow to cool totally before cutting.
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