How to Make It
Line a 9-inch-square baking pan with parchment paper. In a medium saucepan, combine the milk and butter and cook over moderate heat until the milk is hot and the butter is melted. Whisk in the sugar and cook, stirring occasionally, until the mixture reaches 240°, about 5 minutes.
Remove the saucepan from the heat. Add the chocolate, tahini and sesame oil and stir until the chocolate is completely melted. If the mixture separates, whisk in the hot water until it is smooth again. Add the Fluff and vanilla and stir vigorously until the Fluff is completely incorporated.
Scrape the fudge into the prepared pan and smooth the surface. Sprinkle with the toasted sesame seeds and let cool, then refrigerate until cold, about 2 hours.
Cut the fudge into 1-inch squares and sprinkle with sea salt.