Melt chocolate chips over boiling water in a double boiler. Beat egg yolks, adding sugar gradually. Beat until smooth. Beat in butter a little at a time. Dissolve coffee in the Brandy and vanilla. Combine Brandy mixture with the egg and butter mixture. Add melted chocolate and mix thoroughly. Chill well in the refrigerator. Shape into small balls and roll in the pecans. Keep refrigerated. May be frozen and served later.