Preheat oven: Start by preheating your oven to 350°F (175°C).
Melt chocolate: In a microwave-safe bowl, combine the chocolate chips and sweetened condensed milk. Microwave in 30-second intervals, stirring in between until the chocolate is completely melted and smooth.
Mix in vanilla: Stir in the vanilla extract to enhance the chocolate flavor.
Add nuts and marshmallows: Gently fold in the chopped nuts and one cup of mini marshmallows into the melted chocolate mixture.
Fill the pie crust: Pour the mixture into the pre-made chocolate pie crust, smoothing it out evenly.
Top with marshmallows: Sprinkle the remaining mini marshmallows on top of the pie for that decadent finish.
Bake: Place the pie in the oven and bake for about 10-12 minutes, just until the marshmallows are lightly golden.
Cool and serve: Allow it to cool for at least 30 minutes before slicing. Serve as is, or with a dollop of whipped cream!