for the bars
1 1/2 cups butter, cold and cut into pieces
2 1/4 cups white sugar
1 1/2 teaspoons vanilla
1/2 teaspoon kosher salt
2 1/4 teaspoons baking powder
4 1/2 cups all-purpose flour
for the frosting
1/2 cup butter, room temperature
1/4 cup vegetable shorting
1 teaspoon vanilla
1 pound powdered sugar (sifted if from a box)
2-3 tablespoons heavy cream (you can use milk, but it won't be as creamy)
sprinkles, if desired
1. Heat your oven to 350. Line a baking sheet (18x13) with foil and spray with non-stick spray.
2. Cream together the butter and sugar until smooth. Add the vanilla and eggs, one at a time, mixing well after each. Scrape down the sides of the bowl. Add the salt, baking powder, and half of the flour. Mix well and scrape down the sides of the bowl. Add the remaining flour and mix well. Let sit for 15 minutes.
3. Use a muffin scoop or large spoon to scoop the dough out onto the prepared baking sheet. Use your fingers to gently press the dough into an even layer, paying attention to the edges and corners.
4. Bake for 28-30 minutes, or until lightly browned on the top and it feels soft and springy (kind of like a pancake) but not doughy or gooey when you touch the top with your finger. Cool completely before frosting.
5. For the frosting, cream together the butter and shortening. Add the vanilla; mix well and scrape down the sides of the bowl. Add half of the powdered sugar and mix well on medium-low; scrape down the sides of the bowl. Add the remaining powdered sugar and the cream (1 tablespoons at a time) to make the frosting creamy and spreadable. Spread the frosting on the cooled bars and add sprinkles immediately so they will stick.
Makes about 56 bars