Simmer raisins in water. Turn the heat off when the raisins are soft. Add baking soda to raisin water. Cream together sugar, shortening, eggs and vanilla.
In a separate bowl, stir together flour, cinnamon and salt. Add dry to wet mixture and mix until combined. Pour raisin water mixture in small increments into the bowl and mix on low speed until combined.
This makes a lot, so you can either split the batter between a greased 9x13" cake pan AND a greased 8x8" pan OR you can pour and spread it all into a greased 9x13" and just bake it for longer.
Sprinkle 1 cup (I usually use less than that) of brown sugar over the top of the batter and 1 pkg. chocolate chips over the brown sugar. Slightly press into batter.
Bake at 350 degrees for around 30 minutes (if you split the batter between the 9x13 and 8x8), or around 40 minutes for just a 9x13" (cover it with foil so the top doesn't burn because it will take longer to bake) , or until toothpick inserted into center of cake comes out clean. Needs no frosting.