In saucepan, whisk 1 egg until blended. Stir in 2/3 cup sugar, 1/2 cup milk and chocolate. Cook and stir over medium heat until chocolate is melted and mixture just comes to a boil. Remove from heat; cool to room temperature.
In a mixing bowl, cream shortening and remaining sugar. Add remaining eggs, one at a time, beating well after each. Beat in vanilla. Combine the flour, baking soda and salt; add to creamed mixture alternately with remaining milk. Add chocolate mixture; mix well.
Pour into three greased and floured 9 inch pans. Bake at 325 for 25-30 minutes, or until a tooth pick comes out clean. Cool 10 minutes before removing from pans to wire racks.
For frosting, beat cream cheese until light and fluffy. Gradually add milk and peanut butter, beating well after each addition. Spread between layers and over top and sides of cooled cake. Sprinkle with peanuts. Garnish with candy bar squares as desired. Store in refrigerator.