Follow these steps to create your Chocolate Raspberry Sandwich Cookies:

1. Preheat Oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. Mix Dry Ingredients: In a bowl, whisk together the flour, cocoa powder, baking soda, and salt until combined.
3. Cream Butter and Sugars: In a separate bowl, beat the softened butter, granulated sugar, and brown sugar until 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 wet mixture, mixing until a dough forms.
6. Scoop the Dough: Use a tablespoon to scoop out portions of the dough and place them on the prepared baking sheets, leaving space between each scoop.
7. Bake Cookies: Bake in the preheated oven for 12-15 minutes or until the edges are set. The centers may look slightly soft, but they will firm up as they cool.
8. Cool on Racks: Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes. Transfer them to wire racks to cool completely.
9. Prepare Filling: Once the cookies are cool, take half of the cookies and spread a layer of raspberry jam on the flat side.
10. Sandwich the Cookies: Top each jam-covered cookie with another cookie, flat side down, to create a sandwich.
11. Dust with Powdered Sugar: If desired, dust the tops of the sandwich cookies with powdered sugar for an elegant finish.

These steps will guide you in creating Chocolate Raspberry Sandwich Cookies that will surely impress anyone who tries them.