Preheat oven to 325 degrees F. Grease and flour a 9x5x3-inch loaf pan; set aside. In a medium bowl stir together flour, sugar, cream of tartar, salt, and baking soda; set aside.
In a large bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add flour mixture; beat for 2 to 3 minutes or until fine crumbs form.
In a small bowl combine the water and the 1 tablespoon coffee crystals, stirring until coffee crystals are dissolved. Add coffee mixture and vanilla to butter mixture; beat on low speed until combined. Beat on medium speed for 2 minutes. Beat in eggs and melted chocolate on low speed until combined. Beat on medium speed for 1 minute.
Pour batter into prepared pan, spreading evenly. Bake for 75 to 80 minutes or until a toothpick inserted near center of cake comes out clean.
Cool in pan on a wire rack for 10 minutes. Remove from pan; cool completely on rack. If desired, top each serving with Coffee Cream, chocolate curls, and additional coffee crystals.
In a medium bowl combine whipping cream, powdered sugar, and instant coffee crystals. Cover and chill for 10 minutes. Beat with an electric mixer on medium to high speed until stiff peaks form (tips stand straight).