Pre-heat oven to 350 F degrees. In the bowl of a food processor, add pretzel, and pulse small crumbs begin to form. Add brown sugar and melted butte and pulse some more, until all mixed together. Transfer mixture to a 9-inch tart pan, pressing into bottom and up sides.
Bake pretzel crust until set, 10-15 min and let cool completely.
Combine the chocolate, tahini, and kosher salt in a medium bowl.
Heat the cream, vanilla and sweetener of your choice in a small saucepan over medium heat. Once it starts to simmer, remove it from the heat and immediately pour it over the chocolate and tahini. Let it sit for a minute or two to melt the chocolate.
Using a spatula, mix until well blended and no bits of chocolate remain. Get that elbow grease in there! Use quite a bit of elbow grease here — really commit! After a minute or two, the mixture should look thick, glossy, and well mixed.
Immediately pour the filling into the cooled crust and smooth the top.
Whisk cream, tahini and sweetener of your choice and swirl with a spatula on top and sprinkle with flaky salt (or other desired toppings). Let sit for at least 1 hour before slicing.