King Arthur Baking: Oatmeal Cream Pie Bars

I first saw these advertised when I was flipping through Facebook one night.  Darn it, my phone seems to have figured out my preferences.  These looked so fantastic that even though I don't have any particular nostalgia for Little Debbie oatmeal creme pies, I knew they must be made as soon as possible.  So after waiting a couple of days for the Marshmallow Fluff to arrive, I got to savor this simple yet fabulous dessert.

Oatmeal Cream Pie Bars
Adapted from King Arthur Baking

1¼ cups all-purpose flour

1 teaspoon table salt
½ teaspoon baking soda
12 tablespoons unsalted butter, at room temperature
¾ cup dark brown sugar or light brown sugar, packed
⅓ cup granulated sugar
1½ teaspoons ground cinnamon

¾ teaspoon ginger
1½ teaspoons vanilla extract

2 large eggs
1¾ cups quick-cooking oats or instant oats*

*To substitute old-fashioned rolled oats, briefly pulse them in a food processor until each oat is about half its size (several short pulses).

Frosting

¾ cup vegetable shortening or 8 tablespoons unsalted butter, softened
¾ cup confectioners' sugar
1 cup Marshmallow Fluff or 1 cup marshmallow crème, store-bought*
½ teaspoon vanilla extract
1 teaspoon water
¼ teaspoon table salt

*Marshmallow Fluff is a New England ingredient available in certain other parts of the country. Marshmallow crème, more widely available, is a thinner consistency than Fluff. If you make your filling with marshmallow crème, you may need to add a bit more sugar to stiffen it up sufficiently.

Preheat the oven to 325°F. Lightly grease an 8-inch square pan and line with a parchment paper sling.

To make the cookie base: In a medium bowl, whisk together the flour, salt, and baking soda until well-combined.

In a separate large bowl or the bowl of a stand mixer, beat together the butter, sugars, spices, and vanilla, mixing until smooth. Beat in the eggs one at a time, scraping the bowl between additions, until the mixture is smooth, creamy, and thick. Stir in the flour mixture until just combined, then mix in the oats.

Transfer the dough to the prepared pan and smooth it into an even layer with a flexible spatula or an offset spatula.

Bake the oatmeal cream pie bars for 35 to 40 minutes, until the color is a deep golden brown and a toothpick or paring knife inserted into the center comes out clean. Cool for 10 minutes in the pan on the wire rack, then lift out of pan and let cool completely on the wire rack.

To make the frosting: In a large bowl or the bowl of a stand mixer, beat together the shortening or butter, sugar, and marshmallow until well combined. Add the vanilla, water, and salt and beat until smooth.

Spread the frosting on top of the cooled bars, top with sprinkles, and slice into 16 pieces.

Makes 16 squares