In a mixing bowl, whisk together the hot cocoa mix, sugar, cinnamon, and salt until combined. Set aside.

Fill a medium pot almost halfway with water and bring to a simmer over low heat.

Place a heat-safe bowl on top of the pot. Add the white chocolate chips and stir until smooth. Once smooth, add cinnamon and stir to combine. Remove the bowl but leave the water in the pot.

Add a heaping spoonful of the melted chocolate to each of the six molds, spreading the chocolate up the sides. Freeze for 10 minutes, or until completely set.

Line a baking sheet with parchment paper. Carefully remove the chocolate cups from the mold and place them on the lined baking sheet.

Flip over three of the molds and fill each with 2 tablespoons of the hot cocoa mix, ½ teaspoon cinnamon, and 5-6 mini marshmallows.

Place the other three halves seam-side down on a separate baking sheet and place it atop the pot with warm water to slightly melt the rims.

With gloves on, cover each filled half with an empty half, sealing it.

Decorate with any remaining melted chocolate, additional cinnamon, sprinkles, and other cookies or candies. Use immediately or within 24 hours for best results. Store at room temperature.