Line a large sheet pan with parchment paper and set to the side. This will prevent the treats from sticking and make cleanup a breeze.
In a large saucepan over medium heat, melt the salted butter. Be sure to watch it closely to prevent burning; you want it just melted and bubbly.
Reduce the heat slightly and add the marshmallow fluff to the saucepan. Stir continuously over medium-low heat until the marshmallow fluff breaks down and combines into a smooth liquid, taking about one to two minutes. The mixture should be glossy and cohesive.
Whisk in the orange gel food coloring until you achieve your desired vibrant hue. This is your moment to make these treats pop with color!
Once combined, remove the saucepan from the heat. The marshmallow mixture should be warm but not boiling.
Pour the Rice Krispies cereal into the saucepan. Gently stir until the cereal is fully coated with the marshmallow mixture. Be careful not to crush the cereal; you want the texture to remain crispy.
Transfer the orange Rice Krispie mixture onto the prepared baking sheet. Spread it into an even, thin layer using a spatula. Allow it to set aside to cool for about twenty minutes.
While the mixture cools, separate out 12 to 14 chocolate baking chunks to be used as the stems. Cut the M&Ms into halves for leaves.
Once the Rice Krispie mixture has cooled enough to handle, gently scoop it into a large mixing bowl. Spray an ice cream scoop lightly with cooking spray to prevent sticking.
Use the ice cream scoop to press the mixture into large balls, forming the pumpkin shapes. Roll each scoop into a smooth ball and place them back onto the parchment-lined baking sheet.
Now for the fun part! Microwave the remaining chocolate baking chunks in a microwave-safe bowl for thirty seconds, stirring well. Continue heating in fifteen-second intervals until the chocolate is completely melted.
Dip each chocolate baking chunk into the melted chocolate, and gently press it into the top of one of the rice krispie pumpkins. The chocolate adds a lovely touch and richness.
Finally, place two green M&M halves next to the “stem” for leaves. Allow the pumpkins to set for another ten to twenty minutes before serving, letting everything firm up nicely.