How to Make It
Prepare the crust. In a medium bowl, combine the butter, cookie crumbs, and the salt. Press the crumbs into the bottom and sides of a 9-inch fluted tart pan, using a straight-sided dry measuring cup to help. Refrigerate the crust until firm.
Prepare the filling. In a small pot or microwave-safe bowl, heat the cream and butter together until melted. In medium saucepan heat the sugar, syrup, and ¼ cup water over medium-high heat until the sugar turns deep amber, swirling the pan to caramelize the sugar evenly, 6 to 8 minutes. Working gently, remove the sugar from the heat and add the cream mixture. Be careful: this will bubble up and sputter.
Return the saucepan to the stove. Cook the sugar-cream mixture over medium-high heat until it forms a caramel that is thick and smooth, about 3 to 4 minutes. Whisk in the cinnamon and salt and pour the caramel into the prepared crust. Refrigerate the tart until firm, at least 8 hours.
Remove tart from the refrigerator 10 minutes before serving and transfer it to a serving plate. Drizzle tart with melted chocolate and sprinkle with salt. Immediately slice the tart into slices and transfer to plates. Let stand a few minutes at room temperature before serving.