Step 1Heat the oven to 350 degrees. In a metal bowl set over simmering water, melt the chocolate with 1 tablespoon butter, stirring until it is completely smooth. Cool slightly.
Step 2In a mixing bowl, whisk the eggs until light and frothy. Gradually whisk in the sugar until well blended. Add the chocolate mixture and whisk until well blended. Combine the flour, baking soda and salt and gradually whisk into the egg mixture. Add the vanilla and mix well.
Step 3Drop the batter by teaspoons onto greased baking sheets. Bake 8 to 10 minutes, until the cookies are set and crackled on top. Cool on baking sheets before "frosting" each with one-half teaspoon custard.