Melt chocolate and butter together in a small pan over low heat. Stir until the mixture is smooth. Set aside.
In a small cup combine instant coffee granules and boiling water. Stir until smooth.
Add coffee, sugar and vanilla to chocolate mixture and stir.
Using an electric mixer add eggs one at a time, stirring well after each addition.
Add flour and salt. Stir until combined then pour into the prepared baking pan.
Bake in preheated oven for 32-35 minutes.
Cool completely on a cooling rack. Refrigerate or freeze if not continuing the recipe at this point.