Before you've even taken your coat off, put the chocolate and butter in the top of a double boiler above simmering water. Whisk every now and again until melted. In a bowl, whisk together the eggs, sugar, and flour until just blended. Gradually whisk in the melted chocolate mixture. Set aside.
Grease 4 (1-cup) ramekins with butter and add flour to cover the butter, tapping the ramekins to get rid of excess. Preheat the oven to 400 degrees F about half an hour before you want to eat the puddings. And I'd leave cooking them until you've finished the main course. It doesn't matter if there's no food on the table for 10 minutes; and these do have to be done at the last minute.
So, pour the mixture into the ramekins and put them on a baking sheet in the oven for 10 to 12 minutes, until the tops are firm and cracking slightly and the edges set. Serve immediately and consider providing a pitcher of cold, cold cream for people to pour into their pudding's hotly deliquescing interior as they eat.
Recipe courtesy of Nigella Lawson