Spray some cupcake pans with nonstick spray and set aside.
Melt butter in a large pot over low heat.
Add the mini marshmallows to the butter (leaving out the reserved 1 1/2 cups) and stir until melted and smooth.
Remove the pot from the heat, and stir in the 2 packets of powdered hot chocolate mix until fully combined.
Add in the pumpkin pie spice and vanilla and stir until combined.
Working quickly but carefully, gently stir in the crispy rice cereal into the marshmallow mixture until the cereal is thoroughly coated. Gently stir in the reserved 1 ½ cups of mini marshmallows. These reserved marshmallows will make the rice krispie treats extra gooey.
Spray your hands with some nonstick spray or use a little bit of oil or butter to keep the rice krispie mixture from sticking to your hands.
To make the little mug shapes, gently press the rice krispie mixture into the sprayed openings of the muffin/cupcake pans.
Allow the rice krispies to sit in the pans for at least 30 minutes to cool and set.
Once cooled and set, use a butter knife to carefully pop out each of the rice krispie “mugs” from the pans.
Gently break off the two top curves from each of the mini pretzel twists to use for the handles on the rice krispies mugs.
In a microwave-safe bowl, melt the chocolate chips in the microwave on full power in 30-second intervals, stirring between each interval until the chocolate chips are fully melted and smooth.
Dip the ends of the broken-off pretzel curves into the melted chocolate, and attach them to each rice krispie mug by gently pressing them into the sides to create the handles.
Next, using a spoon or small spatula, spread some of the melted chocolate over the center top of one of the mugs to create the look of hot cocoa in the mug. Immediately sprinkle some of the dehydrated marshmallows onto the chocolate so they will stick to the chocolate as it sets. Repeat for each mug until all are complete.
If the melted chocolate starts to thicken while you’re working, simply place it back in the microwave for 10-15 seconds to melt it again.
Sprinkle a little bit of pumpkin pie spice over the tops of each of the mugs for extra pumpkin spice flavor.