Melt chocolate over a double boiler or in the microwave, stirring occasionally until smooth. Sift together flour, cocoa, baking powder, and salt; set aside.
In a medium bowl, cream butter with white sugar and brown sugar until smooth. Beat in eggs one at a time, then stir in coffee crystals and vanilla until well blended. Stir in melted chocolate. Using a wooden spoon, stir in the dry ingredients just until everything comes together. Cover, and let stand for 35 minutes so the chocolate can set up.
Preheat the oven to 350 degrees F (175 degrees C). Line two cookie sheets with parchment paper. Roll dough into walnut sized balls, or drop by rounded tablespoonfuls onto the prepared cookie sheets, leaving 2 inches between cookies.
Bake for 8 to 10 minutes in the preheated oven. Cookies will be set, but the centers will still be very soft because of the chocolate. Allow cookies to cool on the baking sheets for 10 minutes before transferring to wire racks to cool completely.