To prepare a strawberry shortbread bars recipe, first you need to prepare your ingredients. First, you'll need your flour, baking powder, sugar, and salt. Then, add your wet ingredients to the dry ingredients and mix until everything is well combined. Now, it's time to make the filling. You can use any type of shortening you like, but I like to use granulated sugar for this recipe. I used powdered sugar because it is easier to work with and doesn't have the bitter aftertaste that other sweeteners can have. If you want to add any other flavoring, just mix it in before you add it to your batter. Once you have mixed everything together, pour it into your prepared baking pan and bake it for 20 minutes at 325 degrees F or until the top is golden brown. Let the bars cool in the pan for 10 minutes before removing them from the oven to cool completely.