Step 1 Heat the oven to 350 degrees. In the bowl of a stand mixer using the paddle attachment, or in a large bowl by hand, mix together the flour, powdered sugar and butter until they come together to form a dough.
Step 2 Press the dough into a greased 9-inch-by-13-inch baking dish. Bake the crust until golden-brown, about 20 minutes. Remove and cool. Reduce the oven temperature to 300 degrees to bake the bars.