Preheat oven to 350°F and line a large baking sheet with a silicone baking mat or parchment paper.
In a large mixing bowl, beat creamy peanut butter and granulated sugar together until creamy. Add egg and vanilla extract and beat until thoroughly combined.
Roll dough into small balls, using about ½ teaspoon to 1 teaspoon of cookie dough per ball.
Place two balls next to each other on the prepared baking sheet and then using the bottom of a cup or measuring cup, flatten the cookies to ⅛ to ¼ inch thickness.
Dip the tines of the fork into all-purpose flour and press into the cookie to create the criss-cross markings.
Bake cookies for 9 to 11 minutes. Remove from oven, let rest on baking sheet for 5 minutes and then carefully transfer to a cooling rack to cool completely.
While the cookies are cooling, prepare the filling by beating creamy peanut butter, powdered sugar, maple syrup and vanilla extract together.
Spread the filling, about a teaspoon or so per cookie, onto the bottom of one cookie and use the other cookie to make it into a sandwich.
Transfer the cookies to a parchment lined baking sheet and place in the freezer for 10 minutes.
Melt the Ghirardelli chocolate melting wafers according to the package directions until chocolate is completely melted and smooth.
Dip the cookies in the chocolate and place back on the parchment lined baking sheet. Sprinkle with flaky sea salt if desired.
Let chocolate set up completely before serving.
