01 -
Set the oven to 350°F (175°C). Cover two baking trays with parchment paper.
02 -
Stir together the salt, baking soda, and flour in a medium bowl. Put it aside for later.
03 -
Cream the unsalted butter, peanut butter, white sugar, and brown sugar using a big bowl until it's silky smooth.
04 -
Toss the egg and vanilla into the wet stuff, blending until it all comes together. Gradually, stir in the dry ingredients until just mixed.
05 -
Roll dough into balls (about one tablespoon each), then pop them onto the parchment-lined trays with about 2 inches in between. Press down the tops with a fork to make criss-cross patterns.
06 -
Let the cookies bake for 10-12 minutes, or until they just brown around the edges. Let them cool for 5 minutes on the tray, then move them to a rack and cool completely.
07 -
Whip together the powdered sugar, softened butter, peanut butter, and vanilla in a bowl until the mixture is totally blended and creamy.
08 -
Once the cookies are no longer warm, spread some filling onto the flat side of one cookie. Close it with another cookie to make a little sandwich.
09 -
Store these sandwiches in a sealed container at room temperature.