Finely chop the chocolate by placing the block of chocolate on a cutting board

With a chef's knife shave the chocolate into small pieces, starting at one corner

When the cutting surface gets too wide, move to another corner and continue until all the chocolate is chopped

In a medium saucepan combine the corn syrup, whipping cream and cinnamon

Bring to a full boil

Remove from heat and stir in the chocolate until completely melted

Stir in the vanilla

Serve sauce immediately or reheat later.