Line a large sheet pan with parchment paper or a silicone baking mat. Set aside.
In a large pot or dutch oven, add 4 tablespoons of salted butter and stir over medium low heat, until melted. Add 10 ounces of miniature marshmallows and stir until melted.
Add several drops of orange food coloring and stir until incorporated. Remove from heat.
Add 5 cups of rice krispies cereal and gently stir together with the marshmallow mixture until fully combined. Let mixture cool for 15 to 20 minutes or until cool enough to handle.
Cut the green M&Ms in half for the leaves. You can also leave them whole and just press into the pumpkin.
Spray a large cookies coop or ice cream scoop lightly with cooking spray and use it to scoop out the rice krispie mixture and form into large balls, making sure to press the ball together firmly so they hold their shape. Place on the parchment paper.
Place ⅓ cup of semi sweet baking chunks in a small, microwave safe bowl. Microwave in 30 second increments at 50% power, stirring in between, until chocolate is fully melted.
For each pumpkin, dip a chocolate baking chunk into the melted chocolate and then gently press it into the top of one of the rice krispie pumpkins.
Place two green M&M halves next to the “stem” for leaves (dipping in the melted chocolate if they do not stick).
Allow the pumpkins to set up for 10 minutes or so before serving.
