Preheat the oven to 350°F and lightly grease a 9-inch pie dish. Beat the cream cheese and melted butter until mostly smooth.
Mix in the granulated sugar, brown sugar, egg, and vanilla extract until glossy and fully combined.
Fold in the cocoa powder, all-purpose flour, and salt just until no dry streaks remain. Stir in half of the semisweet chocolate chips.
Spread the brownie batter in the prepared dish. Bake for 16 to 18 minutes, until the edges are set but the center remains slightly soft.
Scatter the mini marshmallows and remaining chocolate chips over the hot brownie dip. Broil for 30 to 60 seconds, watching closely, until the marshmallows are toasted.
Let the dip rest for 5 minutes, then serve warm with graham cracker sheets for dipping.