Step 1: Prepare the Lava Filling

1. In a microwave-safe bowl, combine the chopped dark chocolate and heavy cream.
2. Microwave in 20-second intervals, stirring in between, until the chocolate is fully melted and smooth.
3. Let the mixture cool slightly, then refrigerate for 20-30 minutes until it thickens.

Step 2: Make the Cookie Dough

1. In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.
2. In a large bowl, beat the softened butter, granulated sugar, and brown sugar until light and fluffy.
3. Add the egg and vanilla extract, and mix until well combined.
4. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
5. Fold in the chocolate chips.

Step 3: Assemble the Cookies

1. Scoop about 1 tablespoon of cookie dough and flatten it into a disc.
2. Place 1 teaspoon of the chilled chocolate lava filling in the center.
3. Carefully wrap the dough around the filling, sealing it completely. Roll into a ball.
4. Repeat with the remaining dough and filling.

Step 4: Bake the Cookies

1. Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. Place the cookie balls on the prepared baking sheet, spacing them about 2 inches apart.
3. Bake for 10-12 minutes, or until the edges are set but the centers are still soft.
4. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a cooling rack.

Step 5: Serve and Enjoy

1. Serve the cookies warm for the best lava effect.
2. Dust with powdered sugar or serve with a scoop of vanilla ice cream for an extra treat.