Homemade Oreo Cookies

1. In a large bowl, whisk together the melted butter and sugar until well combined. Whisk in the vanilla extract and melted chocolate. Add the egg and whisk until well incorporated.
2. In a separate bowl, combine flour, cocoa powder, salt and baking soda. Then stir the flour mixture into the chocolate mixture. Mix with a wooden spoon until it has a consistency of Play-Doh. Let the dough sit at room temperature for about an hour to firm up.
3. After the dough has firmed up, transfer to a square sheet of parchment paper. Using your hands, shape the dough into a log (about 10 inches long and 2 1/2 inches diameter). Place the log at the edge of the parchment paper and roll the parchment around the log, making sure log is fully encased. Place in the refrigerator for 2 hours, or until firm. Use your hands and re-roll it every 15 minutes or so (still wrapped in paper) to maintain a nice round log.
4. Preheat oven to 325 F. Line a baking sheet with parchment paper. Remove dough from refrigerator, unwrap it and put it on a cutting board. Slice the dough log into 1/4 inch-thick slices. Place slices on the prepared baking sheet with about an inch in between.
5. Bake for 15-20 minutes, or until cookies are firm when touched in the middle. Remove pan from the oven and set it on a rack. Let cookies cool slightly, then transfer to a cooling rack to completely cool before filling.
6. To make the vanilla filling: In a large bowl using a mixer, beat the butter on low speed for about 30 seconds, or until completely smooth and soft. Add the confectioners’ sugar and vanilla, and beat until mixture is perfectly smooth. Add the milk and salt and beat again until smooth. This will yield about a cup of filling.
7. Scoop or pipe about 1 tablespoon of the filling onto the bottom of one cookie. Top with a second cookie, bottom side down. Then press the cookies together to spread the filling toward the edges. Repeat this process until you fill all the cookies.
8. Enjoy!

Adapted from Flour: Spectacular Recipes from Boston’s Flour Bakery + Cafe by Joanne Chang.