In a large bowl or the bowl of a stand mixer, beat 3/4 cup butter and 1/2 cup cream cheese on medium speed with a hand mixer or whisk attachment until smooth.
Next, add 1 1/2 cups granulated sugar and mix on a medium-high speed for a couple of minutes, until the mixture becomes lighter in color.
Add in 1 egg, 2 tsp almond extract (optional), and 2 tsp vanilla bean paste or vanilla extract. Mix on a medium speed until incorporated.
In a separate bowl, whisk together 3 cups flour (use a scale or fluff the flour in the bag, then spoon it into the measuring cup and level it), 1 Tbsp cornstarch, 1 tsp fine salt, and 1/2 tsp baking powder.
Mix the dry ingredients into the butter mixture on a low speed until it is JUST incorporated. Scrape the sides of the bowl with a rubber spatula between additions. At this point, the dough should still be pretty thick and sticky.
Scoop about 2 Tbsp of dough into a separate bowl and mix in 1/2 tsp of cocoa powder until combined and evenly colored. Flatten the dough into a rectangle on a piece of plastic wrap. Wrap the dough tightly and place it in the fridge to chill.
Color the remaining dough green with a generous squirt of neon green. Mix until the dough is just evenly colored. Try not to overmix it! Flatten the dough into a rectangle that's about 1/4 inch thick on a piece of plastic wrap. Wrap the dough tightly and place it in the fridge to chill.
Chill both portions of dough in the fridge for about 30 minutes, in the freezer for 10 minutes, or in the fridge overnight. Preheat the oven to 350°F/175°C right before you start shaping the cookies, and line two large baking sheets with silicone baking mats or parchment paper. It will take a bit of time to shape all the cookies, and that should give your oven enough time to fully preheat. Set aside.
Unwrap each portion of cookie dough so that it's sitting on top of the plastic wrap. Use a 1/4 teaspoon measure to scoop 10 little bits of green dough. Roll each portion into a ball, then pinch one end to look like a Christmas tree branch (see pictures above). Start with the bottom row by placing 4 cookie dough balls together, then 3 for the next layer, then 2, then one (see pictures above).
Then, scoop about 1/8 teaspoon (I fill 1/4 tsp measure halfway) of brown dough and use your hands to roll the dough into the shape of an elongated teardrop. Place this at the bottom of the cookie, in the middle of the four bits of green dough, to look like a tree trunk. Repeat this process, making one tree at a time to prevent the bits of dough from drying out.
The cookies will spread a bit as they bake, so place them at least 2 inches apart. Chill the cut-out cookies (pan and all) one more time in the fridge for an hour or the freezer for 20 minutes to help them keep their shape as they bake.
Bake one sheet of cookies at a time for 14-16 minutes on the middle rack of your oven (bake time can vary based on the cookies' size and the dough's thickness). Keep a close eye on the cookies and be sure to pull them out before the edges start to brown.
Let the baked cookies cool on the pan for about 15 minutes, then transfer to a wire rack to finish cooling.
Drizzle melted white chocolate over each cookie to look like a strand of Christmas tree lights (I put the melted white chocolate in a piping bag to make it easier), then spoon rainbow nonpareils over the white chocolate. Shake off any excess sprinkles, then enjoy!