How do I make my chocolate brownies 'fudgy'?
Every time I make brownies, I always get compliments on how fudgy they are. There may be some variations based on the recipe you use, but the three things I've found to be most important in my experience are:


Don't even think about using a boxed/pre-made mix! Bake from scratch - it adds a whole 3-5 minutes of extra prep time for brownies, but the taste and texture would be worth it even if it added an hour.
Use fewer eggs. I use the King Arthur Flour "Grandmother's brownies" recipe; I can only find an online copy for the 200th Anniversary edition, but those instructions aren't the same as the older version my mom's cookbook has. The recipe calls for 2-4 eggs per batch (a batch is a 9x9" square pan), and instructs you to use more eggs for a cakier brownie, fewer for a fudgier one. I've found that 3 eggs works best for me.
Use brown sugar for at least some of the total sugar in the recipe. The King Arthur Flour recipe calls for 2 cups of sugar, either white or brown. I typically split 50/50; the brown sugar adds a nice flavor, and I think the moisture in it helps achieve that fudgy consistency, too.


There's another element to changing the consistency, too: cooking time. Most brownie recipes I've seen say to bake for 35-45 minutes; I almost never bake them for more than 30 because I find that the edges start to get really dried out. Undercooking slightly will keep the brownies moist and fudgy.

 The ingredients from the old "Grandmother's Brownies" King Arthur Flour recipe: 4 ounces (squares) unsweetened chocolate [can substitute 1-ounce square = 3 tbs cocoa powder + 1 tbs butter); ½ cup (1 stick) butter; 2 cups sugar and/or brown sugar; 2 to 4 eggs; ½ teaspoon salt; 2 teaspoons vanilla; 1 cup flour