Keep the pan size.
A larger pan makes thinner brownies that bake faster; glass may behave differently from metal.
Find a recipe A small pan of cocoa brownies with a dense baked crumb. No chocolate melting step, frosting or extra toppings, with cooling time included before cutting.

Recipe draft · Reviewed editorially, not kitchen tested by us. Prep: about 15 minutes. Cooking: about 30 minutes. Rest: at least 60 minutes, included in the total. Times vary with equipment and ingredient size. Contains wheat, egg and milk. Check cocoa and vanilla labels for other allergens.
Heat a conventional oven to 350°F (175°C). Line an 8 inch (20 cm) square metal pan with parchment, leaving handles over two sides.
Use oven safe parchment and keep loose edges away from heating elements.
Whisk melted butter and sugar together. Add eggs and vanilla and whisk until evenly combined.
Butter should be warm rather than hot enough to cook the eggs on contact.
Sift cocoa, flour and salt into the bowl and fold until no dry streaks remain. Spread into the pan.
Stop when combined. Do not taste raw batter containing flour and egg.
Bake for about 25 to 30 minutes, checking near the end. Extend baking if a tester from the center has liquid batter.
Look for set edges and a tester with moist crumbs rather than glossy uncooked batter. Oven timing varies.
Cool in the pan on a rack for at least 60 minutes, or longer until cool enough to cut cleanly. Lift out using parchment and cut into nine squares.
The 105 minute total includes a 60 minute cooling allowance. Hot brownies crumble more easily.
A larger pan makes thinner brownies that bake faster; glass may behave differently from metal.
Cocoa weights vary by brand. Weighing 45 g is more consistent than packing a measuring cup.