Place the water, chocolates, salt and calcium in a pot and bring to a simmer. When the temperature reaches 90ºC, pour the ingredients into a blender. Turn it on low, and then increase the speed to form a vortex. With the blender still running, carefully remove the lid and sprinkle in the pectin. Run the machine for about five minutes, and then pour the mixture into a plastic-lined dish. Let it cool, undisturbed, at room temperature for 30 minutes. Place in the refrigerator and chill for at least four more hours until completely cool and set. Once the chocolate is cold you can slice it and serve immediately, or cover it with plastic wrap and keep refrigerated until you're ready to serve it.