I'm a fudgy-as-a-truffle gal myself (Alice Medrich's Best Cocoa Brownies are my old faithful, preferably straight from the freezer)—but today, we're not here to discuss that age-old question.
Instead, we're here to take you brownie purists and turn you into brownie hedonists!!!! eccentrics. Your ordinary brownies might be extraordinarily good, but consider these tweaks—in the form of swirls, sprinkles, drops, and swooshes (smears, if you prefer)—for when you want to give your brownie a night on the town, complete with facial glitter (that's still a thing, right?) and a thick coat of mascara.
But also, when you want to clean-out your pantry. Dump out that bag of pretzels, smash them up, and mix them into brownie batter. Or put those Marcona almonds you bought for some thing at some time to rest by mixing them into a caramel sauce and drizzling it over the hot-from-the-oven pan.
Avoid any swirl-ins or add-ons that are very wet (raw banana, for example) if you haven't taken that extra moisture into account. This could make for raw or mushy brownies.
If you're choosing a cakey, high-rising brownie (I don't agree with your decision, but I respect it nonetheless), know that the batter will likely grow above whatever topping you've put on, creating a cobbled effect rather than two distinct layers.
Brownies with so many additions are rich! You'll probably want to cut them a bit smaller than you're used to (which also means you can taste more variations).
Now go brownie bonkers, brownie bananas, brownie bat$h¡t crazy! We certainly did.
Tahini swirl: Make sure your tahini (use white and/or black) is well-blended. I'm a fan of turning on the blender or food processor to re-emulsify the tahini when it's got that clear, oily layer floating on a hard, chalky bottom. Then, blob it over the raw brownie batter in the pan and use a knife or a skewer to create a marble pattern. Finish with a sprinkle of black and white sesame seeds, then bake.
Jam: We used raspberry, but blueberry, strawberry, or cherry would be good, too. And don't forget lemon curd. If your jam is too stiff to swirl, mix in a teaspoon of water until it has a thinner consistency.
Peppermint patties: Chop them into 1/4-inch pieces and evenly distribute them over the brownie batter. They'll melt and spread into fun shapes under the heat of the oven.
Ritz crackers: Crush up buttery Ritz crackers (saltines would work, too!) and sprinkle them over the top of the brownie batter. And here's a fun secret: We actually used the crushed Ritz in place of the flour in Alice Medrich's cocoa brownies, by simply substituting an equal amount of Ritz crackers by weight (65 grams) and plowing forth.
Oreos: Self-explanatory. You can crush them to bits or, do as we did and smash each one gently to maintain the shape of the cookie.
As dreamt up:
Animal crackers, Nilla Wafers, or graham crackers
Dried tart cherries, plumped up in water and drained
Chocolate streusel: We used the topping of Melissa Clark's Chocolate Streusel Pound Cake. Mix 1/2 cup flour with 3 tablespoons of sugar, 1 1/2 tablespoons of cocoa powder, and 1/2 teaspoon of salt. Then rub in 4 1/2 tablespoons of cubed, cold unsalted butter so that you have large crumbs. Stir in 1/3 cup of chocolate chips, chunks, or shavings, then spoon over your brownie batter. This would also be good with a hefty dose of cinnamon and nutmeg.
Peanut butter cookie dough: We stirred together a simple flourless cookie dough (1 cup peanut butter + 1 egg + 1 cup sugar + 1 teaspoon vanilla), added a handful of chocolate chips, and then rolled it into teeny balls that we nestled on top of the brownie batter. They held their shape as the brownies below solidified, which made for delightfully doughy, crumbly mounds perched atop the dense, chocolatey base.
Black bottom: Mix together 8 ounces of softened cream cheese (or goat cheese!), 1/3 cup granulated sugar, and 1 large egg until smooth-ish (petite lumps are okay). Mix in a handful of chocolate chips and spoon all over your pan of raw brownie batter. The cream cheese mixture will relax to cover more of the pan as the brownies bake.
For these applications, you're working with the pan of brownies after it's come out of the oven.
Salted caramel: Make your favorite pourable salted caramel—I used an easy-to-follow recipe from Sally's Baking Addiction—and pour it over the pan of brownies when they've just come out of the oven (that means you'll want to be making the caramel as the brownies bake). Finish with another sprinkle of flaky salt, then set the brownies aside so the glaze sets (and they'll be easier to slice when chilled in the fridge).
Matcha glaze: While the brownies cool, whisk together 1 large egg white, 2 cups of confectioners' sugar, 2 teaspoons of matcha, a pinch of salt, and 1 tablespoon of water. Pour over the room temperature brownies and keep refrigerated (the glaze has a tendency to run). It's a combination inspired by Molly Yeh, and the icing formula comes from Bon Appétit's Matcha Doughnuts.
Nutella fudge: This truly double-decker brownie comes from Marsha's Baking Addiction. Pour a can of sweetened condensed milk into the bowl of a double boiler along with 1 cup of Nutella and 1 1/2 cups of chocolate chips. Stir until melted and smooth, then spread over the cooled brownies and chill until set. Cut into small pieces—these are like candy!
A (former) student of English, a lover of raisins, a user of comma splices. My spirit animal is an eggplant. I'm probably the person who picked all of the cookie dough out of the cookie dough ice cream. For that, I'm sorry.