Melt unsweetened chocolate, 1 cup chocolate chips, vanilla, and butter in a saucepan over low heat, stirring until smooth.

Remove from heat and cool for 10 minutes.

In a bowl, beat eggs and sugar together with an electric mixer for 2 minutes on medium speed.

Beat in the chocolate mixture.

Combine flour, cocoa powder, baking powder, and salt.

Add dry ingredients to the chocolate mixture just until combined.

Stir in the remaining chocolate chips.

Cover the dough and chill for at least 3 hours.

Remove about 1 cup of dough from the refrigerator.

With lightly floured hands, roll the dough into 1-inch balls.

Place the balls 2 inches apart on ungreased or parchment paper-lined cookie sheets.

Bake in a preheated oven at 350°F for 10-12 minutes, or until lightly puffed and set.

Cool on the cookie sheets for 3-4 minutes before transferring to a wire rack to cool completely.

Dust with powdered sugar.