Trace around an 8×8 baking pan with parchment paper, leaving about an inch on all sides. Generously butter the parchment paper and place it as securely as possible inside the pan.
In a small saucepan, heat the condensed milk, butter, honey and cinnamon. Keep an eye on this mixture: once the butter has melted, turn off the heat. At the same time, insert your kitchen thermometer (optional) into a medium saucepan, combine sugar with 2 1/2 tablespoons of water. Place over medium-high heat and let the sugar dissolve. Stir gently to be sure that the sugar melts smoothly. From this point on, stir only as necessary. Cook until the sugar reaches 300 degrees, or for 5-7 minutes.
Remove from heat and add the cinnamony milk and butter to the sugar mixture. Cook the caramel over medium heat until it reaches 245 degrees, or for 3-5 minutes.
Remove the medium saucepan from the heat. Add vanilla extract.
Pour the mixture into the prepared baking pan, carefully as to not scrape the hard bits on the bottom and sides. While letting the caramel cool for up to 15 minutes, melt chocolate chips over low heat. Spread the chocolate over cooled caramel. Sprinkle fleur de sel as a garnish.
Once completely cool, lift out of the pan and onto a countertop. Slice the bar of caramel with a long, sharp knife.