In a large bowl, cream shortening and sugar until light and fluffy. Add chocolate and vanilla; mix well. Add eggs, one at a time, beating well after each addition. Combine the flour, baking soda and salt; add to creamed mixture alternately with buttermilk. Fold in the chocolate chips. Pour into three greased and floured 9-in. round baking pans. Bake at 350° for 30-35 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely. For frosting, in a large bowl, cream butter until light and fluffy. Combine sugar and cocoa; add to creamed mixture alternately with milk. Add vanilla; beat well. Spread frosting between layers and over top and sides of cake.