Combine the graham cracker crumbs with the melted butter and a pinch of salt in a mixing bowl, stirring until the mixture is evenly coated and crumbly.
Press the crumb mixture firmly into the bottom of a greased 9x13 inch baking pan, creating an even, compact crust. Chill in the refrigerator while you prepare the marshmallow layer.
Spread the marshmallows evenly over the chilled crust, making sure to cover all areas for a gooey topping.
Place the pan under the broiler, watching carefully as the marshmallows puff up and turn golden brown—this should take about 2-3 minutes. Remove once toasted and set aside to cool slightly.
In a microwave-safe bowl, melt the chocolate chips with the vanilla extract in 30-second intervals, stirring until smooth and glossy.
Pour the melted chocolate mixture over the toasted marshmallow layer, spreading it evenly with a spatula for a glossy, drippy finish.
Allow the bars to set at room temperature for about 1 hour, or refrigerate for quicker firming. Once the chocolate is firm and the marshmallow is slightly sticky, slice into squares and serve.