• Preheat oven to 350ºF. Line a 9x13 cake pan or baking dish with foil or parchment paper. If useing foil spray with cooking spray (preferable with flour in it!)
• In the bowl of a stand mixer, or a large bowl if using a hand mixer, beat together the butter and cream cheese until smooth. Add in the sugar, and mix well, scraping down the sides of the bowl, as necessary.
• Add the egg and vanilla and mix. 
• Add the flour, baking powder, and baking soda and mix on low speed until a soft dough forms. 
• Spread the dough evenly into your prepared pan (use your hands, the bottom of a glass, etc. if necessary to make it easier!) Bake for 20 minutes. Remove from oven and cool completely, before frosting.

For the Peach Buttercream Frosting:

• In the bowl of your (cleaned out) stand mixer, using the whisk attachment, whisk the butter until smooth. Mix in the vanilla. 
• Add the powdered sugar, one cup at a time, with 1 tablespoon of the peach syrup and the heavy cream until all the ingredients have been added and the frosting is smooth, scraping down the sides of the bowl as you go. Taste and add an additional tablespoon of peach syrup if you would like a stronger peach flavor. 
• Spread the frosting evenly over the cooled cookie base and add the sprinkles. Cut into squares (I did 4x5 rows, but you could do 4x6 for a little smaller squares, to make 24 bars!) Serve and enjoy!