Line a 9×9″ pan with parchment paper or foil (leave enough to hang over the edges). Set aside.
Combine the sweetened condensed milk, chocolate chips and butter in a large pan over medium-heat. Stir until the chocolate has melted. Turn the heat to low and stir in the cinnamon and taco seasoning. Once the chocolate is smooth and creamy, stir in the marshmallow cream and mix until smooth.
Remove pan from heat and allow to cool for 3 minutes. Then stir in the mini marshmallows and pour the mixture immediately into the pan. Sprinkle sea salt on top if desired. Let the fudge set for at least one hour.
Remove the fudge with the parchment paper and then slice into 36 bars. Enjoy!
Notes
To speed up the cooling process, you may place the pan in the freezer after it has already cooled for 15 minutes.You can substitute chili powder in place of taco seasoning if preferred.