In heavy saucepan or microwave, melt broken chocolate with half and half; set aside to cool.
In double boiler, over simmering water, beat egg yolks with hand mixer.
Gradually add sugar, beating on high until creamy.
Add Marsala, stirring to heat slightly.
Beat on high until mixture starts to thicken.
Remove from heat and continue beating until very thick.
Stir 1/2 cup of egg yolk mixture into chocolate; fold the two mixtures together.