Rinse and dry the orange and zest it. Set the zest aside and save the orange for another use. Grease a 9x13-inch pan with cooking spray.
In a large pot, melt the butter on the stove over medium-low heat.
Add the marshmallows to the pot and stir constantly until they are fully melted. This could take at least five minutes. Turn off the heat and move the pot to a cool burner.
Stir in the zest and orange extract until combined. Add the Rice Krispies to the pot and stir until fully blended with the marshmallow mixture.
Carefully transfer the cereal mixture to your pan. It helps to grease a silicone spatula with cooking spray and use it to spread the mixture evenly. Use your hands to gently press the cereal into place.
When the cereal mixture is cooled off a bit, spread on the Nutella in an even layer. Garnish with extra orange zest, if desired.
Cut into squares and serve. Store leftovers covered at room temperature for up to five days.
The orange extract adds a nice pop of flavor. You can take it down to ¼ teaspoon, if you prefer it more subtle. And, if you don’t have the extract, the Nutella Rice Krispie treats will still be delicious.
A 13-ounce jar of Nutella is just enough to thinly frost a 9x13 pan of these treats. I probably used 19 ounces when I made these for the photos. Use as much Nutella as you’d like, but they’ll obviously be sweeter (and messier) with more.