Line an 8×8” baking pan with foil leaving a 1” overhang; lightly spray the bottom.
In a bowl, whisk together the flour, powder, soda and salt – set aside.
In a large bowl stir together the butter and brown sugar until combined. Mix in the egg and vanilla stirring just until incorporated. Or if you’re making the Angelic version, stir together the coconut oil and splenda. Mix in the egg whites and vanilla.
Stir in the zucchini and gently mix.
Add in the dry ingredients and with a mixing spoon, mix just until combined.
Add in the cranberries & white chocolate chips (sinful version only) and gently fold in.
Scrape the batter into the prepared pan and spread evenly.
Bake for 27-32 minutes or until an inserted cake tester comes out with just a few crumbs. Do not overbake.
Remove the pan from the oven and place on a cooling rack. Allow to cool completely in the pan.
While the bars are cooling make the buttercream.
In a stand mixer fitted with the paddle attachment, beat butter for 5 minutes on medium until light in color.
Shut the mixer off and add 3 cups of confectioners’ sugar.
Turn your mixer on to the lowest speed (trust me, if you don’t, you’ll end up with a face full of sugar and dust!)
Mix until the sugar has been fully incorporated with the butter.
Increase the speed to medium and add vanilla, salt, and 2 tablespoon of milk.
Beat for 3 minutes until light and fluffy.
If your frosting needs a stiffer consistency, add the rest of the sugar.
Grabbing the foil overhang, lift the bars out of the pan and place on the counter.
Gently pull back the foil from the sides.
Cut the bars into 16 pieces and spread buttercream on each individual piece. Again the buttercream is only for the Sinful version.