Peanuts and peanut butter pack extra peanutiness into these flourless cookies, and their saltiness is the perfect balance to the brown sugar. For a sure bake sale sellout, take them to the next level by dunking half of each cookie into melted chocolate.
Preheat the oven to 350 degrees. Line 2 cookie sheets with parchment paper.
Place the peanut butter, sugar, eggs, and baking soda in a large mixer bowl and beat until smooth and creamy, about 3 minutes. Stir in the chopped peanuts.
Using a heaping small (2-teaspoon size) cookie scoop, drop the dough about 1½ inches apart on the prepared cookie sheets. Top cookies with chocolate sprinkles, if using.
Transfer to the oven and bake until the edges of the cookies are lightly browned, 10 to 12 minutes, rotating the cookie sheets on the oven racks halfway through the baking time. Cool on the cookie sheets for 5 minutes. Transfer to wire racks and cool completely. Repeat with the remaining dough on cool cookie sheets.
Store in an airtight container for up to 3 days, or freeze for up to 3 months.