Preheat your oven to 350°F (175°C). Line your muffin tin with paper liners.
In a mixing bowl, combine cream cheese, 100g granulated sugar, salt, egg whites, and sour cream. Beat until smooth, then stir in chocolate chips.
In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, and salt. In another bowl, mix sour cream, water, melted butter, and vanilla extract. Gradually add wet to dry ingredients, stirring until just combined.
Spoon about 1.5 tablespoons of chocolate batter into each muffin cup, add 1 tablespoon of cream cheese filling, and top with another 1.5 tablespoons of chocolate batter.
Bake for 20-25 minutes or until a toothpick comes out clean.
Cool in the tin for 10 minutes, then transfer to a wire rack to cool completely.