Use a 15 cm loose-bottomed round pan and line it with parchment paper, wrapping it in aluminum foil. Preheat the oven to 160°C to get it ready for baking.

Crack 4 room-temperature eggs into a bowl. Separate the yolks from the whites (save one extra yolk for later use) and set aside.

In a saucepan, heat 150g cream cheese, 50g sugar-free milk, and 25g unsalted butter on low heat until dissolved. Transfer the cream cheese mixture, sift in 40g flour (or cornstarch), and whisk well. Then, fold in 3 egg yolks.

Beat the egg whites with an electric mixer, starting at low speed and moving to medium until foamy. Add 50g sugar in 3 batches, continuing until soft peaks form.

Gently mix a third of the beaten egg whites with the yolk mixture. Then, fold the rest together, making sure to preserve the air pockets for a fluffy texture.

Pour the batter into the pan, smooth the surface, and tap to remove bubbles. Set the pan in a water bath (using foil to prevent leaks) to ensure even baking and reduce cracking.

Bake for 25 minutes at 160°C, then reduce the temperature to 100°C for another 60 minutes. Keep the oven door ajar during the last 30 minutes to prevent cracking, and let the cheesecake cool in the oven for an additional 30 minutes before removing.