Preheat oven to 425F

Soften the butter by letting it sit at room temperature for 40 minutes or microwave for about 15-20 seconds. Add powdered sugar and mix with a hand mixer for about a minute.

Add the peanut butter, egg white, vanilla extract, salt and continue mixing for another minute or two. Add flour and continue mixing until flour is fully incorporated.

Line a large baking sheet with parchment paper. Place the dough into a disposable pastry bag with a large star tip and pipe cookies onto the baking sheet. The cookies should be about 2 inches in diameter.

Using a wet finger, gently press in the center of each cookie, about 3/4 of the way. These dimples will be filled after baking is done. Bake at 425F for about 8-10 minutes, until the sides of cookie are starting to turn golden brown.

Meanwhile, combine the peanut butter, powdered sugar and sea salt in a bowl and mix with a hand mixer until smooth and fluffy, about 1 minute.

Let the cookies cool down. Pipe the filling in the middle of each cookie. Serve and enjoy.