Beat creamy peanut butter and unsalted butter on medium speed until smooth.
Add granulated sugar and brown sugar and continue beating until pale and fluffy.
Add egg and vanilla until mixed.
In a separate bowl whisk flour, baking soda and sea salt.
Add flour mixture to peanut butter mixture 1/2 cup at at time, beating on low until combined. As you go, scrape down the sides of the bowl with a spatula to incorporate all ingredients.
Cover dough and chill in the refrigerator for 1 hour
Using a 1-inch cookie scoop, scoop dough into balls. Place cookies on a parchment-lined baking sheet spaced 2 inches apart. Using your thumb, make a shallow indent on the top of each dough ball and fill the each indent with 1/4 tsp of jam.
Cover cookies and refrigerate for 2 hours.
Once chilling time is complete, preheat oven to 350 degrees. Remove cover from chilled cookies and bake until lightly brown, 11 to 13 minutes.
Cool on cookie sheet for 5 minutes before transferring to a wire rack to cool completely. If desired, add more jam and/or drizzle with melted peanut butter for decoration.
Cookies stored at room temperature in an airtight container will last up to 1 week.