Preheat oven to 350. Oil a 13 x 9 inch baking pan, set aside.
In a large bowl, sift together the flour, sugar, cream of tartar, baking soda, and salt. Stir in the chocolate chips, set aside.
In a medium bowl, combine the oil, soy milk, applesauce, and vanilla, stirring until smooth, set aside.
In the top of a double boiler or in a medium metal bowl set over a pot of gently simmering water, melt the chocolate, stirring just until smooth.
Add the oil mixture to the flour mixture, stirring until smooth. Add the melted chocolate, stirring until smooth. Stir in the vinegar.
Transfer the batter to the prepared pan and smooth the surface. Bake for 40-45 minutes until the cake springs back when lightly touched in the center and begins to pull away from the sides of the pan. Thoroughly cool on a cooling rack before frosting with Fudgy Chocolate Frosting.