Step 1: Prepare Baking Pan: Preheat oven to 350F (175C). Grease and flour an 8x8 inch baking pan, or line it with parchment paper, leaving an overhang for easy removal.
Step 2: Combine Wet Ingredients: In a large bowl, combine the melted butter, eggs, and water. Whisk until well combined and the mixture is smooth. Ensure the butter is not too hot, as it could cook the eggs.
Step 3: Incorporate Cake Mix: Add the chocolate cake mix to the wet ingredients. Gently fold together until just combined. Avoid overmixing, as this can result in tough brownies. A few streaks of dry mix are acceptable.
Step 4: Add Chocolate Chips (Optional): If desired, gently fold in the chocolate chips into the brownie batter.
Step 5: Transfer to Pan: Pour the brownie batter into the prepared baking pan. Spread evenly to ensure uniform baking.
Step 6: Bake: Bake in the preheated oven for 23-28 minutes, or until a toothpick inserted into the center comes out with moist crumbs. The baking time may vary depending on the oven.
Step 7: Cool and Cut: Let the brownies cool completely in the pan before cutting into squares. Cooling allows the brownies to set properly, making them easier to slice neatly. If using parchment paper, lift the brownies out of the pan using the overhang and place them on a cutting board.
Optional: For fudgier brownies, slightly underbake them. For cakier brownies, bake them a bit longer. Substitute vegetable oil for melted butter if preferred. Add a teaspoon of vanilla extract for extra flavor.