In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Mix until well incorporated and resembles wet sand. Press firmly into the bottom of a 9×13-inch pan to create the crust.

In a large mixing bowl, pour the heavy whipping cream and beat with an electric mixer on medium-high speed until stiff peaks form, about 3–5 minutes.

In another bowl, beat together softened cream cheese, confectioners' sugar, and vanilla extract until smooth and creamy, about 2 minutes. Fold half of the whipped cream into the mixture.

Spoon the cream cheese mixture over the prepared crust, spreading it evenly. Scatter mini marshmallows on top.

Melt the semi-sweet chocolate chips and milk in a microwave-safe bowl. Heat in 30-second intervals, stirring in between, until melted and smooth.

Pour the melted chocolate over the mini marshmallows, spreading it evenly.

Spread the marshmallow crème over the chocolate layer, smoothing it out for an even top.

Gently spread the reserved whipped cream on top of the marshmallow crème.

Cover with plastic wrap and chill for at least 4 hours or overnight.

Slice into squares and serve, optionally garnishing with extra graham cracker crumbs or chocolate chips.