Step 1: Make the Chocolate Cookies

1. Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
2. In a large bowl, beat butter, brown sugar, and granulated sugar until fluffy (about 2 minutes).
3. Add eggs and vanilla extract, mixing until smooth.
4. In another bowl, whisk together flour, cocoa powder, baking soda, and salt.
5. Gradually mix the dry ingredients into the wet ingredients until combined.

Step 2: Bake the Cookies

1. Scoop tablespoon-sized dough balls onto the prepared baking sheets, spacing them 2 inches apart.
2. Bake for 8-10 minutes, until the edges are set but the centers are still soft.
3. Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Step 3: Make the Peanut Butter Filling

1. Beat peanut butter and butter until smooth.
2. Gradually add powdered sugar, mixing until fluffy.
3. Add vanilla extract and heavy cream, if needed, to reach a creamy consistency.

Step 4: Assemble the Cookies

1. Spread or pipe 1-2 tablespoons of peanut butter filling onto the flat side of a cookie.
2. Top with another cookie and gently press to create a sandwich.
3. Enjoy immediately or chill for 30 minutes for a firmer texture.