Pre-heat oven to 325 degrees
Butter 9 x 5 x 3 inch loaf pan and dust if with fine bread crumbs
Put chocolate and instant coffee in a small bowl and add water until it melts. Let cool.
Sift flour, baking soda and salt
In a large bowl, cream butter, add vanilla and brown sugar and beat to mix well. Add eggs one at a time. Then add the dry ingredients until incorporated and then add the sour cream. Finally, add the cooled chocolate on low speed.
Pour the batter into the prepared pan and bake for 60 to 70 minutes until a tooth pick comes out clean.
Let the cake cool and then invert the cake and let it cool on a rack.