Preheat oven to 350°F. Spray two 8 x 2-inch baking pans with vegetable pan spray.
Melt 1 cup chocolate chips and butter together either in microwave oven or on top of range over low heat. Stir until chocolate is completely melted. Pour into large bowl.
Add sugar; beat with electric mixer on low until well blended. Beat in eggs, one at time. Add vanilla. Stir in 1/2 cup flour, baking soda and salt; mix well. Add remaining flour and water; mix until smooth. Stir in remaining 1 cup of chocolate chips.
Pour into prepared pans.
Bake 35-40 minutes or until toothpick inserted in center comes out clean. Cool in pan on cooling rack 10 minutes. Remove from pan; cool completely.
Meanwhile, prepare filling and icing. In large bowl, cream shortening and butter with electric mixer until light and fluffy.
Add vanilla; mix well. Gradually add sugar, one cup at a time, beating well. Scrape sides and bottom of bowl often.
When all sugar has been mixed in, icing will appear dry. Add milk, 1 tablespoon at a time; beat at medium speed until light and fluffy.
Reserve 1 1/2 cups white icing. Beat melted chocolate into remaining icing.
Keep icing covered with a damp cloth until ready to use.
Place 1 cake layer on cake board or serving plate; spread with white buttercream icing. Arrange 2nd cake layer over bottom layer.