Cream butter. Gradually add sugar in mixer. Blend in melted chocolate when it is fairly cool. Add vanilla. Add eggs, one at a time, beating 5 minutes at medium speed after each egg. After completing adding eggs, check consistency. It should taste smooth -- not grainy. If it still tastes grainy, beat longer until smooth. (That's very important!) Turn into cooled baked pie shell. Chill overnight. (Do not freeze.) Whip the cream and cover pie and garnish with chocolate shavings before serving.