I start by lining my 8-inch pan with parchment paper, leaving a little overhang on the sides.

In a small saucepan, I combine the raspberries, sugar, and a splash of water over medium heat. I mash the berries as they cook and let the mixture bubble for a few minutes until it thickens slightly into a glossy sauce.

I always pour my sauce through a fine mesh strainer to get rid of the seeds. It takes an extra minute, but it gives me a much smoother, more elegant swirl once it hits the batter.

In a larger saucepan, I melt the butter and chocolate chips together over low heat, stirring constantly so nothing scorches. Once it's silky smooth, I take it off the heat and let it cool slightly before moving on.

While the chocolate cools, I whisk my room-temperature eggs with the sugar and vanilla in a separate bowl until the mixture looks pale and slightly frothy. This step builds a little air into the batter.

I slowly stream the egg mixture into the cooled chocolate, stirring the whole time. Going slow here is key, since pouring it in too fast can accidentally scramble the eggs in the warm chocolate.

I sprinkle in the flour, salt, baking soda, and baking powder, then fold everything together just until no streaks of flour remain. I try not to overmix so the brownies stay dense and fudgy.

I spread the batter evenly into my prepared pan, then spoon small dollops of raspberry sauce across the top. Using a butter knife, I drag it through the dollops in swooping motions to create that classic marbled swirl.

I bake my brownies at 350°F for about 30 minutes, watching for the edges to look set while the center still has a slight jiggle. A toothpick should come out with a few moist crumbs, not wet batter.

This is the hardest step for me, but I let the brownies cool fully in the pan before lifting them out and slicing. Cutting too early makes them fall apart instead of holding those clean, fudgy squares.