Melt the chocolate over low heat and set aside to cool. Sift the flour, baking powder, baking soda, salt, and sugar together into a large mixer bowl. Add the brown sugar, two third cup of sour milk, shortening, vanilla, and red food coloring to the dry mixture. Beat on medium speed for 2 minutes, scraping the sides of the bowl several times while beating. Add the cooled chocolate, one third cup of sour milk and the eggs and continue to beat, at medium speed, for an additional 2 minutes, or until well blended. Scrape the sides of the bowl frequently. Pour into two 23 cm prepared round cake pans. (Prepare by greasing and flouring pans.) Bake in a preheated 375 degree oven for 30 to 35 minutes or until the cake tests done. Cool in the pan for 5 minutes and turn out on wire racks to finish cooling until cold. Frost.