Salty-Sweet Peanut Butter Sandies

cup/228 grams/2 sticks unsalted butter, preferably cultured, softened at room temperature

cup/150 grams granulated sugar

(packed)/170 grams light brown sugar

heaping teaspoon/6 grams kosher salt

cups/510 grams unsweetened peanut butter, creamy or chunky

eggs, at room temperature

cups/250 grams all-purpose flour

Flaky sea salt and coarse sugar for sprinkling (or use kosher salt and granulated sugar)