Preheat oven to 350°F.
Make the Cookie Bars: Whisk the flour, baking powder, baking soda and salt to a small bowl and whisk.
Add the softened butter and sugar to a large bowl and use an electric mixer to beat until light and fluffy (3-5 minutes).
Add the eggs, vanilla bean paste, almond extract and cream cheese. Beat to fully incorporate. Slowly add the dry ingredients and and beat in to incorporate—but only until no streaks of flour are seen. If you want sprinkles in your cookie bars, add the sprinkles with the last bit of dry ingredients. Don’t over mix at this time.
Line a 9x13 inch baking pan with parchment. Press the cookie dough evenly into the pan. The dough will be a bit sticky. I sprayed my hands lightly with oil to help with this. Laying a piece of parchment over it helps as well.
Bake for about 20-25 minutes, or until the edges are lightly browned and the center is set and no longer wet. The edges tend to a bit less gooey than the center, like a brownie would be, and it’s ok if the center still seems a touch under done because as it cools, it sets up nice. Allow to cool completely.
Make the Frosting: (If you plan to make the Christmas trees, double the frosting ingredients)To make the frosting, beat the softened butter until smooth and creamy. Add the vanilla, sea salt and almond extract and mix to incorporate. Slowly add 2 cups of the powdered sugar and beat until combined. Add the cream, one tablespoon at a time and beat until creamy and fluffy. Add green food coloring (about 5 drops was used for the green in photos) and mix to incorporate. If making the trees, you may need to add a touch extra cream too.
For classic cookie bars: Frost the cookie bars and add extra sprinkles over top. Allow the buttercream to set before cutting.
For Christmas tree bars: Remove the fully cooled cookie bars from the pan by pulling out using the excess parchment as tabs. Slice off the ends and then slice a row of bars, then cut back and forth at a diagonal to create triangle pieces.
Add the buttercream to a piping bag or plastic bag with desired piping tip and decorate by piping in rows or get creative! Allow frosting to set and serve!