Brownies: Prepare the brownies according to package directions in a 8×8 or 9×9 pan. Use melted butter as a substitute for oil.
Ganache: Add chocolate chips to a microwave-safe bowl with the cream. Microwave for 1 minute. Whisk until smooth and shiny. If there are still lumps, microwave for an additional 30 seconds. Spread 2/3 of the ganache over the cooled brownies. Add 3 tablespoons cream to the remaining 1/3 of the ganache and whisk until well incorporated.
Honey Roasted Cornflakes: Add the cornflakes to a baking sheet and drizzle with honey. Stir until the cornflakes are well coated. Bake at 350°F for 5 minutes. Carefully remove from the oven and sprinkle with flakey sea salt and toss until well coated. Bake an additional 5 minutes. Working quickly, carefully spoon the cornflakes over the layer of ganache as soon as you pull them from the oven. Spread them evenly over the ganache so it is covered evenly. Press down lightly into the chocolate. Drizzle the remaining chocolate over the cornflakes. Allow the layered brownies to cool to room temperature before serving.