Step 1: Prepare the brownie batter according to the box instructions.

Step 2: Pour half the batter into a lined baking dish and drizzle with half the caramel, swirling with a knife.

Step 3: Pour the remaining batter over the top, drizzle with remaining caramel, and swirl again.

Step 4: Sprinkle cornflakes evenly over the top, pressing gently so they stick.

Tip: Press gently rather than stirring in, so the cornflakes stay crunchy.

Step 5: Bake according to the box instructions, until a toothpick comes out with a few moist crumbs.

Step 6: Let cool, sprinkle with sea salt, then slice and serve.