Step 1

Spray the bottom of a 9" tart pan or pie pan with non-stick spray and place a circle cut out of parchment paper in the middle of the pan. Spray the parchment paper and side of the pan again and set aside.

Step 2

Add the butter to a large pot. Once the butter has melted, stir in 1 bag of marshmallows until it is melted and combined with the butter on medium-low heat. Take the pot off of the stove and mix in the vanilla and salt into the melted marshmallow mixture.

Step 3

Place the Rice Krispies, Fruity Pebbles, and 1/2 bag of marshmallows into the pot and combine thoroughly.

Step 4

Spoon the mixture into the tart pan and press down with a greased spatula to level. Wait 1 hour before adding toppings.

Step 5

While the rice krispie treats set, make the marshmallow buttercream frosting. Place the butter and powdered sugar in a large mixing bowl and beat together until fluffy, about 1-2 minutes.

Step 6

With a silicone spatula, fold in the marshmallow fluff and vanilla. Combine thoroughly. You can also add a few drops of food coloring in pastel colors into the frosting.

Step 7

Once the rice krispie treats are set, spoon the marshmallow frosting into a piping bag. Starting at the center of the pan, pipe frosting onto the rice krispie treats in a circular motion until the edges are reached. Place additional Fruity Pebbles and Marshmallow Peeps atop the frosting and serve immediately.