Preheat your oven to 350°F (175°C). Line a standard 12-cup muffin tin with cupcake liners or lightly grease each cup to prevent sticking.
In a medium bowl, combine the brownie mix, vegetable oil, eggs, and water. Stir until the batter is smooth and fully blended, but avoid overmixing to keep the brownies tender.
Using a spoon or cookie scoop, fill each muffin cup halfway with brownie batter. Make sure the batter is evenly distributed to ensure consistent baking.
Drop about one tablespoon of caramel sauce into the center of each muffin cup. Follow with a sprinkle of chopped nuts over the caramel, pressing them slightly into the batter for a good layer.
Cover the caramel and nuts with the remaining brownie batter, filling each muffin cup almost to the top. Sprinkle chocolate chips evenly over each cup.
Bake the brownie cups for 18-22 minutes, or until a toothpick inserted near the edge comes out with just a few moist crumbs. Remove from oven and immediately sprinkle sea salt over the warm tops. Allow them to cool in the tin for 10 minutes before transferring to a wire rack to cool completely.
