In a stand mixer fitted with the paddle attachment, cream together unsalted butter and granulated sugar on medium speed until light and fully combined, about 2–3 minutes.

Add egg yolks and pure vanilla extract; beat until smooth and homogenous.

With the mixer on low, add all purpose flour and salt. Beat until the dough just comes together and holds when pressed.

Divide the dough in half, shape each portion into a log about 1 1/2–2 inches in diameter, wrap tightly in plastic wrap, and chill for at least 45 minutes.

Preheat the oven to 350°F (175°C) and line baking sheets with parchment.

Unwrap the chilled logs and slice into 1/4-inch slices, reshaping if necessary. Arrange the slices about 1 inch apart on the prepared baking sheets.

Bake for 11–13 minutes, until the edges begin to brown and the centers set. Cool on the sheet for 10 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat unsalted butter (room temperature) with creamy peanut butter until smooth and silky.

Add sifted powdered sugar and pure vanilla extract; beat until the mixture is firm enough to pipe.

Pipe or spread a dollop of the peanut butter filling onto the underside of one cooled cookie; sandwich with another cookie.

Refrigerate the sandwich cookies until the filling firms, about 20–30 minutes.

Melt the chocolate wafers in a microwave-safe bowl, heating in 20–30 second intervals and stirring until smooth.

Dip each chilled sandwich cookie halfway into the melted chocolate, let excess drip off, and place on parchment. Drizzle remaining chocolate for a pretty finish.

Let set completely at room temperature or refrigerate briefly to speed solidification.