Preheat the oven to 350 degrees F. Line several baking sheets with parchment paper and set aside.
In an electric stand mixer, add the softened butter and both sugars. Beat on high to cream the butter and sugar for 3-5 minutes, until very light and fluffy.
Meanwhile, set out another mixing bowl. Measure and dump in the flour, baking powder, baking soda, and salt. Mix well. *When measuring flour, stir to fluff the flour in the bag, scoop or spoon it into measuring cups, then level each cup.
Place the dry roasted peanuts in the blender (or food processor) and pulse to grind them into fine powder. Do not pulse them so long that they turn into natural peanut butter. You want fine peanut crumbs!
Once the butter mixture is fluffy, scrape the mixing bowl with a rubber spatula. Then beat in the peanut butter, eggs, and vanilla until very smooth.
Turn the mixer on low and add in the flour mixture, one scoop at a time. Once incorporated, scrape the bowl again. Then beat in the ground peanut crumbs, and immediately turn off the mixer. (It's important to not overmix the dough, or it will become tough.)
Portion out even 2-tablespoon balls of dough. Place the balls (or mounds) on the baking sheets 2 1/2 inches apart. They do not have to be perfect balls, but you do want them to be the exact same size/weight.
Set out a glass of water. Dip a large table fork in the water. Then press the cookie tops with the fork to create a criss-cross pattern. Press the cookies just enough that they are flat and crossed on top, but do not let them get thinner than 3/4 inch.
Bake for 9-10 minutes per batch. The cookies will look a little under-baked when you take them out of the oven, but the edges should be firm and crisp. Let the cookies cool on the warm baking sheets for 5 minutes before moving.
Baking Mishaps: Most baking errors occur in measuring, or due to faulty oven thermostats. It's very normal for ovens to run too hot or cool up to 50 degrees! Consider buying a new oven thermometer once a year, to better regulate your oven temperature.