Preheat oven to 350°F
In a large bowl with an electric mixer (a paddle attachment on a stand mixer works best for this recipe), beat peanut butter and butter until smooth.
Add both white and brown sugar and beat on high speed until light and fluffy, about 2-3 minutes.
Add eggs and vanilla and beat on low speed just until combined.
Add flour, baking soda, and salt and beat on low speed just until the dough comes together.
Roll into 1" balls and place 2" apart on baking sheets. Press down slightly with a fork in a criss-cross pattern. (optional: roll the cookie balls in white sugar before pressing down with the fork)
Bake for 10-12 minutes, just until set
Remove and let cool on baking sheets.