Cream together butter sugar, eggs and vanilla until fluffy (beat 5 minutes at high speed on mixer, scraping bowl occasionally to guide batter into beaters; or beat 5 minutes by hand). Blend in cooled chocolate. Sift together flour, soda and salt; add to creamed mixture alternately with ice water, beginning and ending with flour, beat after each addition. Bake in a paper lined 9" x 1-1/2" round pan in moderate oven 350 degrees (30 t0 35 minutes or until done.)
Frost with Chocolate Satin Frosting
3-1/2 (1 ounce squares) unsweetened chocolate
3 cups sifted powdered sugar
4-1/2 tablespoons hot water
1/2 cup soft butter
1-1/2 teaspoons vanilla
Melt chocolate in mixing bowl over hot water. Remove from heat. With electric mixer blend in sugar and water. Beat in egg, then butter and vanilla. Frosting will be thin at this point, so place bowl in ice water; beat until spreading consistency. Frost tops and sides of two 9" layers.