These are baked from a very slightly modernized version of a chocolate cookie recipe believed to be the first chocolate cookie recipe ever baked in the United States.
Melt the chocolate in the microwave or in a double boiler.
While the chocolate is cooling off just a little bit, food process the almonds and sugar until the almonds are very finely ground.
Add the almond paste, powdered sugar, and chocolate to the food processor and process until very well blended. Stop to scrape down the sides of the processor when necessary. (Nancy's instructions say that this step should take 2-3 minutes. Mine was completely blended at about one minute.)
Add the egg whites and vanilla and process in on/off pulses until the mixture stiffens and the processor motor labors. If it's still not thoroughly mixed (mine was), turn out the dough to a medium-sized bowl and stir until well blended.
Refrigerate the dough for at least two hours or overnight.
Preheat the oven to 325 F.
Roll teaspoon-sized balls of dough in the chopped almonds.
Place on parchment or Silpat-lined cookie sheets, spacing about one inch apart.
Bake for 10-14 minutes or until barely firm when pressed in the center.
Slide the sheet of parchment or the Silpat with the cooked cookies onto a cooling rack (being careful not to burn yourself).
Once cool, remove cookies and store in an airtight container for up to four days or freeze for up to one month.