Heat the oven to 375 °F and line two baking sheets with parchment. Whisk the flour, baking soda and salt in a medium bowl.
Beat the butter, peanut butter and both sugars in a large bowl until smooth, about 2 minutes. Beat in the egg and vanilla.
Add the dry ingredients and mix on low just until combined. Roll the dough into 1-inch balls (about 1 tablespoon each), roll in the extra sugar and place 2 inches apart on the sheets.
Bake 8-10 minutes, until the edges are set and the tops are crackled.
Press one unwrapped chocolate kiss into the center of each cookie right away. Cool on the sheet 5 minutes, then transfer to a wire rack.
