CHOCOLATE SYRUP: Combine all ingredients in a small saucepot, add ¾ cup water, and bring to a simmer over medium heat. Simmer mixture 3 to 4 minutes, whisking occasionally, or until it is thick and smooth. Cool completely and store in the refrigerator in an airtight container for up to 1 month.

MARSHMALLOW FLUFF: Combine corn syrup, sugar, and ¼ cup plus 2 tablespoons water in a medium saucepot and bring to a simmer over medium heat. Cook until mixture reaches 240°F on a candy thermometer, about 10 to 15 minutes. While mixture is simmering, place egg whites in the bowl of stand mixer fitted with the whisk attachment. Beat on medium speed until egg whites are foamy, about 2 minutes. Increase speed to medium-high and add cream of tartar and salt. Continue to beat until soft peaks form.

Once sugar mixtures reaches 240°F, remove from heat and let rest for about 20 seconds. Increase the stand mixer speed to high and, slowly stream sugar mixture into the egg whites, trying not to let the sugar mixture hit the whisk or the sides of the bowl. Once all the sugar is added, scrape down the sides of the bowl with a spatula to ensure sugar mixture is fully incorporated, then continue to mix for 7 to 8 minutes, or until the outside of the mixing bowl returns to room temperature. Add vanilla and whisk for 1 minute longer. Use immediately or store in an airtight container in the refrigerator for up to 2 weeks.

MILK: Whisk together milk and syrup in a large bowl. Using the back of a tablespoon, smear small mounds of the marshmallow fluff around the rim of a tumbler glass. Using a blowtorch, gently brûlée the marshmallow fluff until it is browned but not burnt. Add chocolate milk to the prepared glass and enjoy.