Line crock pot with parchment paper or spray lightly with non-stick cooking spray.
In a mixing bowl, combine the properly measured flour, salt and cocoa powder. Stir together with a spoon until mixed. Set aside.
In a small saucepan over low heat, combine the chopped unsweetened chocolate and softened butter. Stir occasionally until it’s fully melted, about 5 minutes.
Meanwhile, in a larger mixing bowl, beat the sugar and eggs plus additional egg yolk with an electric mixer for 1 minute, until the mixture is pale yellow and doubled in volume.
Once the chocolate is melted, pour it into the egg mixture. Then add the vegetable oil and vanilla extract. Stir with a spatula to combine.
Spoon the flour mixture into the wet ingredients, mixing with a spatula just until combined. Do not continue to mix the batter once you can no longer see flour.
Reserve 1/3 cup of the batter.
Add the remaining batter to the crock pot. Set aside.
In a mixing bowl, combine the cream cheese, sugar and egg, beat using an electric mixer until smooth, 1-2 minutes.
Drizzle the cream cheese filling in a grid pattern, then use a butter knife and drag it across the grid to create swirls.
Add in the remaining 1/3 cup of batter where you see fit. Swirl again with the knife.
Cook for 3 hours on HIGH. Turn off crock pot and let rest for 30 minutes.
Allow the brownies to cool completely before cutting.