Heat oven to 375°F; parchment-line two sheets. Beat butter, peanut butter, brown sugar, and dough granulated sugar smooth.
Beat in egg and vanilla. Whisk flour, baking soda, and salt; mix into dough just until combined.
Form 30 balls; roll in remaining sugar and space 2 inches apart. Unwrap chocolates before baking.
Bake one sheet at a time 9 to 10 minutes until bottoms lightly browned. Immediately press one chocolate into each center.
Cool on sheets 10 minutes; carefully transfer to rack until chocolates firm again.