Line a baking sheet with parchment paper and set aside. To a medium saucepan, add the sugar, butter, kosher salt, ground cinnamon, and vanilla extract over medium/ low heat, stirring occasionally to incorporate ingredients and ensure you don’t end up with a greasy mess. Insert a candy thermometer and bring the mixture to 285° Fahrenheit on a candy thermometer. The mixture should be a nice, amber color. Remove the pan from heat and working very quickly pour the pretzels into the toffee and stir to incorporate.  Pour the mixture over the parchment lined baking sheet and flatten as best you can. Allow to cool completely and break into pieces. Drizzle melted chocolate, if desired. Store pieces between squares of parchment.