Spread a dollop of butter along the bottom and edges of a 9 X 13" pan.
Measure out 4 cups of marshmallows and set aside and reserve.
In a large saucepan, over low heat, melt butter (10 tablespoons). When the butter is melted add the marshmallows (excluding the 4 reserved cups) and continue to cook, stirring constantly, until marshmallows are just melted. Remove from heat and stir in vanilla (1 ½ teaspoons) and salt (½ teaspoon). Gently fold in fruity pebbles and coat evenly, then fold in the reserved 4 cups marshmallows.
Spoon mixture into the prepared pan and gently press into an even layer. Let the mixture come to room temperature and set. Then cut and serve.
Notes
Butter: Because these are not baked, instead of using the nonstick cooking spray I use butter to coat the dish. I like the itty bit of butter flavor this adds rather than the nonstick stuff!
Can I use salted butter for fruity pebble treats? Yes! In fact, this is one of those rare times where salted butter is my preference. The salted butter cuts through the sweetness of these bars and creates a better balance of flavor.
Mini Marshmallow - When you make these treats, use fresh marshmallows! Don't use a bag you find in the back of your pantry that you bought 2 years ago!! Old marshmallows dry out and won’t produce the gooey texture you want in this recipe. Friends, just buy some fresh bags.
Vanilla Extract: Always use the real stuff rather than imitation.
Light touch: Have you ever had traditional rice Krispie treats that are hard and solid like a rock. Well, there's a super easy trick to keep them delightfully chewy and gooey, simple very gently press mixture into the prepared pan. If you must you can very gently use a buttered spatula to slightly even the top out. I skip that step and live with a perfectly imperfect form to keep them as gorgeous delicate texture. Never press the mixture firmly into the pan!
Time saver: If you'd rather, you can melt the butter and marshmallows in the microwave. You'll have to experiment a bit with timing as I prefer to make them on the stovetop because everything can be made in one pot, so I haven't worked out exact microwave times!
I mean, who has a microwave-safe bowl large enough to melt the butter and marshmallows then toss 12 cups of cereal in without ending up with a huge mess? I also find stovetop cooking lets me monitor the temperature more carefully. Scorched marshmallows = extreme sadness!!
Stir Well! After adding the cereal, be sure to fold and mix everything really well to coat. The mixture is very thick and will require gentle strength to achieve. If you don’t dig down to the bottom of the mixture, as the bars cool, there will be parts that don’t get covered with marshmallow coating.