Preheat oven to 350 degrees and line a baking sheet with parchment paper.
In the bowl of a standing mixer with a paddle attachment, combine the peanut butter and sugar on medium speed for about 1 minute.
Turn off the mixer and scrape down the sides of the bowl. Add egg, yolk, vanilla, salt and baking soda. Mix on medium speed until well combined, about 2 minutes.
Use a tablespoon to scoop out 18 even balls of batter. Roll each ball gently in the palms of your hands and place onto lined cookie sheet. Leave about 1 1/2 inches between each cookie to allow for spreading while baking.
Press a few pieces of chocolate into each cookie and sprinkle with a little more sugar.
Bake for 10-12 minutes or until light golden brown. Cool slightly, then remove cookies with a spatula to a wire rack to finish cooling.