In a medium bowl, mix the room-temperature cream cheese with a pinch of salt until mostly smooth. You do not want to whip air into the cream cheese; just mix until there are no large lumps remaining.

Fold in the melted white chocolate until fully combined. The mixture should be fairly smooth and thick.

Line a baking sheet with parchment paper or a silicone baking mat. Transfer the cream cheese mixture to the prepared baking sheet and use an offset spatula to spread it into a thin, even layer.

Freeze for about 1 hour, or until firm and solid enough to handle.

Preheat the oven to 350°F. Line an 8-inch square metal baking pan with parchment paper, leaving enough overhang on two sides to lift the brownies from the pan once cooled.

In a microwave-safe bowl, combine the butter and semisweet chocolate. Microwave in 30-second increments, stirring well between each with a nonstick spatula, until completely melted and smooth. Set aside to cool slightly.

Pour the warm melted butter and chocolate mixture into the egg mixture. Add the vanilla extract, white vinegar, and red food coloring, then mix until smooth and evenly combined.

If either cocoa powder is clumpy, sift it through a fine-mesh sieve before adding it to the batter. Add the natural cocoa powder, Dutch-process cocoa powder, flour, and salt, and fold just until no dry streaks remain.

Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. If the toothpick comes out coated in wet batter, continue baking for a few more minutes. For fudgier brownies, remove them when a few moist crumbs still cling to the toothpick rather than waiting for it to come out completely clean.