You'll make the cookie dough, then split it into 3 portions if you want vanilla, medium chocolate, and a dark/black chocolate. Adjust how much dough you'll want of each color or a mix when making the cow print. If you want them all cow-print, you'll only need 1/8-1/4 of the dough to be chocolate, as you'll then add small pieces to the top of the vanilla cookie dough and roll it smooth, then cut the cow shape with a cookie cutter.
Preheat the oven to 400°F.
In the bowl of an electric mixer, mix the butter until smooth, whipped, and light in color for at least 2 minutes.
Add in the powdered sugar and mix to combine with the butter.
Add in the egg and vanilla and mix on medium until combined.
Add in 2 1/2 cups flour, baking powder, and salt, and mix until smooth on medium to medium-high speed, the dough will pull away from the sides of the mixing bowl.
Split the dough into the portions you want. Add 1-2 tablespoons of cocoa (one at a time) to the portions and mix by hand to combine or use the mixer. Add in another tablespoon if needed for the desired color/flavor. (I take a piece off and taste it)
Add a tablespoon or two of flour (one at a time) to the vanilla cookie portion if you need it a little firmer, and mix well to combine.
You don't want the cookie dough to be dry, as the dry ingredients will absorb the moisture from the butter as you mix it. If by chance any of the cookie dough portions become too dry, add a tablespoon or less of soft butter to your hands and knead it into that portion of dough.
Roll the cookie dough to 1/4" thick. I use two 1/4" dowels and place the rolling pin on top to be sure all the cookies will be an even thickness.
When making the cow-print versions, place the vanilla cookie dough and roll it smooth, then add small pieces of chocolate cookie dough on top, then roll it smooth, then place teh cookie cutter in flour, then cut the cookie dough.
Place the cut cookie dough onto parchment-lined baking sheets.
Bake for 7-9 minutes, until the cookies are firm and golden in color on the bottoms.
Remove the cookies from the oven, and allow them to cool on the baking sheets.
Completely cooled cookies can be wrapped and stored at room temperature for 5 days, or wrapped well and frozen for 2 months.