Heat oven to 350°F. Grease and flour two 9-inch round baking pans.
Stir together sugar, flour, cocoa, baking powder and salt in large bowl. Add eggs, milk, oil and vanilla; beat on medium speed of electric mixer 2 minutes. Stir in boiling water. Pour batter into prepared pans.
Bake 30 to 35 minutes or until wooden pick inserted in center comes out almost clean and the top springs back when touched gently. Cool 10 minutes; remove from pans to wire racks. Cool completely.
3/4 cup (1-1/2 sticks) butter
1 cup Hershey's Cocoa
4 cups powdered sugar
1/2 cup milk
2 teaspoons vanilla extract
Place butter in large mixer bowl. Add cocoa, stirring until smooth.
Gradually beat in powdered sugar, milk and vanilla, beating until smooth. If necessary add additional milk, a teaspoon at a time, beating until spreading consistency. About 3 cups frosting.