Step 1: To make the chocolate lava filling, finely chop the dark chocolate and place it in a heatproof bowl. Heat the liquid whipping cream in a small saucepan until it just begins to simmer.
Step 2: Pour the hot cream over the chopped chocolate. Let it sit for 2-3 minutes, then stir gently until smooth and glossy. Cover and refrigerate for 30-60 minutes, or until firm enough to scoop.
Step 3: For the cookie dough, in a large bowl, whisk together white sugar, unsweetened cocoa powder, and vegetable oil.
Step 4: Beat in eggs one at a time, followed by vanilla extract and salt until smooth.
Step 5: In a separate bowl, whisk together all-purpose flour and baking powder. Gradually add dry ingredients to wet, mixing until just combined.
Step 6: Cover and chill the cookie dough in the refrigerator for at least 1 hour, or until firm enough to handle.
Step 7: Preheat oven to 175°C (350°F). Line a baking sheet with parchment paper.
Step 8: Take a tablespoon of chilled cookie dough, flatten it, place 1/2 teaspoon of chilled ganache in the center, and enclose it to form a ball. Ensure the ganache is fully sealed.
Step 9: Roll each dough ball generously in confectioner's sugar, ensuring a thick, even coating.
Step 10: Place coated cookie balls 2 inches apart on the prepared baking sheet.
Step 11: Bake for 13-15 minutes. The cookies will be slightly soft in the center and will set as they cool.
Step 12: Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.