Melt the chocolate in a double boiler and set aside to cool.
Sift together the flour, baking powder, salt soda and mace and set aside.
In a large bowl cream the butter, add the vanilla and sugar and mix well. Beat in the egg and then the chocolate.Gradually add the sifted dry ingredients and beat only until everything is incorporated.
Shape the dough into a slightly flattened disc and wrap airtight and refrigerate for a few hours.
Adjust two racks to divide the oven into thirds and preheat oven to 375° F (190°C).
Line cookie sheets with aluminum foil.
Work with half of the dough at a time, keeping the other half refrigerated if the kitchen is very warm. Roll, cut, etc. Dough can be rolled as thin as 1/16th of an inch if you want, but then will be fragile and should be baked for less time.
Bake for 12-15 minutes or until semi-firm to the touch. Sprinkle lightly with additional sugar. Cool slightly; remove from cookie sheet to wire rack. Cool completely.
This recipe doubles well.
Measuring the Baking Soda:
To measure 1/16 tsp. baking soda: fill and level 1/4 tsp. then with a small metal spatula or table knife mark it into equal quarters, cut away three quarters (returning it to the box), and use the remaining quarter.
Date: October 23, 2002