Preheat your oven to the temperature specified on the Ghirardelli brownie mix package (typically around 325°F or 160°C for a metal or glass pan).
Lightly grease your chosen baking pan.
In a medium bowl, combine the Ghirardelli brownie mix, water, vegetable oil, and the egg.
Stir these ingredients well until everything is just blended. Be careful not to overmix the batter.
Pour the brownie mixture into your prepared pan and spread it evenly to the edges.
Bake for the time recommended on the box, usually between 30-35 minutes. To check for doneness, insert a toothpick near the center; it should come out with moist crumbs, not wet batter.
Allow the baked brownies to cool completely in the pan before slicing. This helps them set properly and makes for cleaner cuts.
Enjoy your homemade Ghirardelli brownies!