Line a loaf pan with plastic wrap.
Chop the chocolate and place it in a bowl suitable for the microwave. Heat in pulses of 20 seconds, stirring between to not burn the chocolate. You can also melt on Bain- Marie (double boiler).
When the chocolate is completely melted, add the tahini, and mix well.
Pour onto the prepared pan, and *optional* sprinkle with salt.
Transfer to the freezer to harden for about 4 hours.
Cut into small cubes or scoop into small balls and coat with cocoa powder (like truffles).
Keep frozen.