1. Preheat your oven to 180°C (350°F). Line a muffin tin with 12 cupcake liners.

2. In a heatproof bowl, combine the cream cheese and sour cream. Place the bowl over a pot of simmering water (double boiler) and whisk until smooth and well combined.

3. Remove the bowl from heat and add 40g of sugar, mixing well. Then, add the egg yolks one at a time, whisking thoroughly after each addition.

4. Sift the all-purpose flour into the mixture and stir until smooth. Gradually add the milk and mix until fully incorporated.

5. In a separate clean bowl, beat the egg whites until foamy. Gradually add the remaining 50g of sugar and continue to beat until soft peaks form.

6. Gently fold one-third of the meringue into the cream cheese mixture to lighten it. Then, carefully fold in the remaining meringue until the batter is homogeneous, being cautious not to deflate the mixture.

7. Divide the batter evenly among the prepared cupcake liners, filling each about 3/4 full.

8. Place the muffin tin in a larger baking pan and add hot water to the outer pan to create a water bath.

9. Bake for 20-25 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out clean.

10. Remove from the oven and allow the cupcakes to cool in the pan for a few minutes before transferring them to a wire rack to cool completely.