1 (1 ounce) square unsweetened chocolate
3/4 cup butter
3/4 cup white sugar
1 teaspoon vanilla extract
1 1/2 cups all-purpose flour
1 teaspoon baking powder
1 pinch salt
1 tablespoon orange zest
Preheat the oven to 175 degrees C. In a microwave-safe dish, melt the unsweetened chocolate, stirring frequently until smooth. Set aside.
In a medium bowl, cream together the butter and sugar until smooth. Beat in the egg and vanilla. Combine the flour, baking powder, and salt; stir into the creamed mixture. Divide dough in two. Mix orange zest into one half, and melted chocolate into the other half. Use a bit of each mixture to form a ball about 1 inch in diameter.
Bake for 8 to 10 minutes in the preheated oven, or until center is set. Cool on wire racks.