In a large bowl or the bowl of a stand mixer, beat 1 cup (2 sticks) unsalted butter and 1 ¼ 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 large egg, 1 tsp vanilla bean paste or vanilla extract, and 1 tsp almond extract (optional). Mix on a medium speed until incorporated. Scrape the sides and bottom of the bowl with a rubber spatula as needed.
Then, add 3 cups of flour, 1 tsp cornstarch, 1 tsp baking powder, and 1 tsp fine salt to the butter mixture and mix at a low speed until it is JUST incorporated. Scrape the sides and bottom of the bowl with a rubber spatula to make sure everything is properly mixed together.
At this point, the dough should still be pretty sticky. Divide the dough into three equal-sized portions (about 10 oz. each). Leave one uncolored, and use gel food coloring to color one portion green, and the other red. Wrap each portion of dough in a piece of plastic wrap. I like to flatten the dough out into a rectangle that's about ⅓ inch tall to make it easier to roll out once it's chilled. Try to make sure the cookie dough portions are similar in size to make it easier to stack them together later.
Chill the dough in the fridge for about 30 minutes, in the freezer for 10 minutes, or in the fridge overnight. If you chill the dough overnight, let it sit out at room temperature for about 5 minutes before trying to roll it out. This will make it easier to roll out.
Preheat the oven to 350 F / 175 C 30 minutes before you plan to cut the cookies, and line two large baking sheets with silicone baking mats or parchment paper. Set aside.
Unwrap each portion of cookie dough and lay the plastic wrap flat on your counter. We will be rolling out the cookie dough on the plastic wrap to make cleanup a breeze and to make it easier to cut the cookies.
Roll out each portion of chilled dough to be about 6x12 inches and then stack the dough in the following order: green, white, red. Trim the edges with a sharp knife to get rid of any uneven pieces. Then use the rolling pin to gently roll over the three layers of cookie dough to make sure they stick together.
Carefully roll the cookie dough into a long log. I find that pulling up the plastic wrap and using it to help roll the cookie dough onto itself makes the process easier. Pour 1 cup of Christmas sprinkles into a rimmed baking sheet and roll/press the cookie dough in the sprinkles until it's fully coated.
Use a sharp knife to slice cookies that are about ¼ inch thick. Place the cookies on the prepared baking sheets, spacing them about 1 inch apart. The cookies will spread a bit as they bake so they need a little room.
Bake one sheet of cookies at a time. Bake for 12-14 minutes on the middle rack of your oven (bake time can vary a lot based on the size and thickness of the cookies). Rotate the pan halfway through to help them bake more evenly. Keep a close eye on the cookies and be sure to pull them out before the edges start to brown. When in doubt, err on the side of undercooking! The cookies will continue to firm up on the pan as they cool. The end pieces always end up looking a bit wonky once they're baked, so I consider those my taste-test cookies! Let the cookies cool on the pan for 15 minutes, then move them to a wire rack to finish cooling.
Let the baked cookies cool fully on the pan, then enjoy! These can be stored in an airtight container at room temperature for up to 5 days.
