Let’s walk through the process of making these cookies, step by step, just as I would with my kids by my side, eager to lick the spoon:

1. Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
3. In a large bowl, cream the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy, about 3 minutes.
4. Add the egg and vanilla extract to the butter mixture, mixing until well combined.
5. Gradually mix in the dry ingredients until the dough forms. Be careful not to overmix.
6. Fold the chopped bittersweet chocolate into the dough, ensuring it’s evenly distributed.
7. Scoop about 2 tablespoons of dough and shape it into a ball, placing a few semi-sweet chocolate chips in the center. Seal the dough around the chips, forming a cookie ball.
8. Place each cookie ball onto the prepared baking sheet, leaving enough space between them for spreading.
9. Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are still soft.
10. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Serve warm for that gooey, lava-like center.