Creating these Chocolate Raspberry Sandwich Cookies is a fun and satisfying process. Follow these steps for the best results:

1. Preheat Your Oven: Begin by preheating your oven to 350°F (175°C). Line two baking sheets with parchment paper.

2. Prepare the Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.

3. Cream the Butter and Sugar: In a larger bowl, cream the softened butter and granulated sugar together until the mixture is light and fluffy.

4. Add Egg and Vanilla: Beat in the egg and vanilla extract until well combined.

5. Combine Mixtures: Gradually add the dry ingredients to the butter-sugar mixture. Mix until just combined; do not overwork the dough.

6. Chill the Dough: Cover the dough with plastic wrap and refrigerate for 30 minutes to help it firm up.

7. Form the Cookies: Once chilled, scoop tablespoon-sized amounts of dough and roll them into balls. Place them on the prepared baking sheets, leaving space between each cookie.

8. Bake: Bake in the preheated oven for 10-12 minutes. The cookies should look firm around the edges but soft in the center.

9. Cool the Cookies: Remove from the oven and let them cool on the baking sheets for 5 minutes before transferring them to wire racks to cool completely.

10. Prepare the Raspberry Filling: In a mixing bowl, mash the fresh raspberries with a fork. Add the powdered sugar and lemon juice, mixing until smooth. Gradually beat in the softened butter until well combined.

11. Assemble the Sandwich Cookies: Take one cooled chocolate cookie and spread a teaspoon of raspberry filling on the bottom. Place another cookie on top, bottom-side down, to create a sandwich. Repeat this process with the remaining cookies.

12. Garnish (Optional): Drizzle with melted chocolate or dust with cocoa powder for an extra touch.

By following these steps, you will create exquisite Chocolate Raspberry Sandwich Cookies that are sure to impress!