Bring the milk, sugar, and butter to a boil in a skillet over high heat, stirring often to incorporate.
Bring to a boil, then cook for another five minutes over medium heat.
Whisk in the chocolate chunks until they are melted after taking the liquid from the stove.
Add the marshmallow fluff and vanilla essence, whisking until combined.
Once the baking dish is prepared by lining it with aluminum foil and spraying it with cooking spray, pour the ingredients into it.
Chill for at least a few hours before serving.
Savor it!