Preheat the oven to 350°F. Line 2 baking sheets with Silpats or parchment paper and set aside.

In the bowl of an electric mixer fitted with the paddle attachment, cream the butter, peanut butter, salt, and sugars together on medium-high speed until light and fluffy, 3 to 4 minutes. Add the egg and vanilla and mix on medium speed until well combined.

In a medium mixing bowl, sift the flour and baking soda together. Add this dry mixture to the butter mixture and beat just to combine. Add the salted peanuts, reserving 2 tablespoons for sprinkling on top, and beat just until combined.

Scooping out the dough with 2 tablespoons, shape the dough into balls and place them 3 inches apart on the prepared baking sheets. Dip the tines of a fork in warm water and press the dough balls lightly with the back of the fork to flatten them slightly (dip the fork back in the water for each dough ball, to prevent sticking). Sprinkle each cookie with the remaining crushed nuts and a few grains of Himalayan or Maldon sea salt.

Bake, rotating the baking sheets between the oven shelves halfway through baking, until golden brown, 18 to 20 minutes.

Transfer the baking sheets to a wire rack to cool. Store the cookies in an airtight container for up to 1 week.