1. In a food processor or blender, whirl chocolate until finely chopped. Pour into a bowl. Put eggs and yolks in the processor or blender.
2. In a 4-cup glass measure, heat whipping cream in a microwave oven (see Notes) at full power (100%) until cream boils, 3 to 5 minutes.
3. With processor or blender on high speed, add boiling cream to egg. Check temperature of mixture with an instant-read thermometer; if below 160°, pour mixture back into glass measure and reheat in microwave oven at full power until it reaches 160°, stirring and checking at 15-second intervals.
4. Combine hot cream mixture, chopped chocolate, and liqueur in blender or processor (or whisk the ingredients together in a large bowl); whirl until smooth, about 1 minute.
5. Pour chocolate mixture into 8 ramekins or glasses (1/2-cup size). Chill until softly set, 30 to 45 minutes. If making ahead, cover and chill up to 1 day. For creamiest texture, let desserts stand at room temperature about 30 minutes before eating.
6. Spoon 1 tbsp. wafer crumbs onto each pot de crème. Insert a Tombstone Cookie into each serving.
Note: Nutritional analysis is per serving with 1 Tombstone Cookie.
This method uses a microwave to heat the cream until it's hot enough to cook and thicken the eggs, but you can always make it on the cooktop. Heat the cream over medium-high heat until it boils, about 6 minutes. Proceed with step 3, but heat the cream-egg mixture as needed in the saucepan until it reaches 160°. Then proceed with step 4.