|Unsweetened baking chocolate squares||4 Ounce (4 Squares, 1 Ounce Each)|
|Margarine||1 Cup (16 tbs)|
|Flour||2 Cup (32 tbs), sifted|
|Baking soda||1 Teaspoon|
|Brown sugar||1 1⁄2 Cup (24 tbs)|
|Sweetened rhubarb sauce||1 Cup (16 tbs), drained (Slightly Sweetened)|
|Unflavored yogurt||1⁄2 Cup (8 tbs)|
|Walnuts||1 Cup (16 tbs), coarsely chopped|
1) Preheat the oven to 350° F.
2) In a heavy pan, melt the chocolate with 1/2 the margarine over a very low heat, stir continuously; allow to cool.
3) In a bowl, sift the flour, baking soda and spices together.
4) In a bowl, cut rest of margarine into the sugar with a pastry blender.
5) Then gradually beat in the eggs, one at a time, mix well.
6) Stir in the melted chocolate, vanilla and rhubarb, blend well.
7) Alternately add the flour mixture and yogurt, beat until smooth after each addition.
8) Stir in the walnuts and mix until evenly distributed.
9) In a grease 9 X 13-inch baking pan, lined with a waxed paper, spread the batter evenly at the bottom.
10) Bake in the preheated oven for about 35 minutes; allow to cool in the pan and stand overnight.
11) Frost the cake with the chocolate cream frosting, if desired.
12) Slice and serve on a serving platter.