1 cup cold water
1 1/2 cups white sugar
1 3/4 cups instant coffee powder
1/2 cup packed light brown sugar
1 teaspoon salt
3 egg yolks
2 tablespoons all-purpose flour
1 teaspoon vanilla extract
3/4 cup bittersweet chocolate chips
3/4 cup milk
1 tablespoon butter
In a large mixing bowl, combine cold water, sugar, instant coffee powder, and brown sugar. Stir into the sugar mixture. Stir in the flour, vanilla and chocolate chips. Continue to stir until the mixture forms a ball, about 5 minutes. Drop by tablespoonfuls onto waxed paper lined paper towels to drain.
Line a roasting pan with a damp kitchen towel. Place tins of chocolate and milk in hot water to boil, then place water aside to cool. Melt chocolate and milk in large skillet over low heat, stirring constantly until smooth. Remove from heat and whisk chocolate and milk into bowl; immediately remove from refrigerator. Stir in tins of melted chocolate mixture and vanilla. Stir in 1 cup flour, 1/2 cup semisweet chocolate chips, and 1 tablespoon butter to melt. Fold in chocolate mixture until no streaks remain. Let warm.
Pour into prepared pan each cup of hot chocolate mixture 1 cup at a time, making sure to spread evenly. Place each cup of hot chocolate into a shallow baking pan, lightly oiled. Cover and refrigerate for 1 hour, or until firm. Frozen chocolate may be stored until 3 days, or overnight, before serving.