Candy Corn Pebbles™ are a new limited-edition version of Pebbles cereal. It's packed with candy corn goodness. These easy whoopie pies are perfect for sharing and sure to liven up any Halloween party spread!
Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper, or use an ungreased whoopie pie pans.
In a large bowl of an electric mixer, beat the butter on medium to high speed for 30 seconds. Add the sugar, baking soda, and salt. Beat until combined, scraping the bowl occasionally. Beat in the egg and vanilla until combined.
Alternately add the flour and buttermilk, beating on low speed after each addition just until mixture is combined. Drop the dough by rounded tablespoons into the wells of the whoopie pie pan or 2 ½-inches apart onto the cookie sheet. Sprinkle the cereal in the center of half of the cookies. (The cookies without the cereal will be the bottom half of the whoopie pies, the cookies with the cereal will be the tops.)
Bake until the edges are firm, 7 to 8 minutes. Cool on a cookie sheet for 2 minutes. Transfer the cookies to a wire rack; cool completely.
While the cookies are cooling, prepare the filling. In a large mixing bowl using an electric mixer, combine the sugar, butter, crushed cereal, marshmallow fluff, and vanilla. Beat on medium speed until smooth. Refrigerate until ready to assemble the cookies. Spread the bottom of one of the cookies with the filling. Place another cookie on top of the filling, bottom-side down. (Use the cookies with the Candy Corn Pebbles as the tops of the whoopie pies.)
Store, covered, in the refrigerator for up to 1 week.