1. Prepare the cake pan : Brush the base and the sides of a 18cm cake pan with a little of the melted butter. Line the sides and the bottom with parchment paper. For the side, the paper height might be a bit higher than the mold as the cheese cake will rise. Tip : If you use a loose-bottomed cake tin, then also wrap the bottom of the tin with double sheets of foil, so as to seal it completely. But I recommend to use not a loose-bottomed one...
2. Making the bottom of the cake Put the flour, sugar, salt, coffee powder and butter in the food processor. Pulse several times to mix until the dough comes together.
3. Spread the cookie mix or roll it out on the baking sheet appropriately and bake for about 20 mins at 170C degree. Remove from the heat and press the cookie mixture into base while it is hot (otherwise it will be too hard once it cools down). Set aside.
4. In a medium size bowl, using a rubber spatula, mix together cream cheese and sugar (40g) until it becomes smooth.
5. Add the egg yolks one at a time and mix them each time.
6. Sift cake flour on it and mix well until incorporated with a egg whisk. Add the melted butter and mix. Then add grated parmesan cheese (optional) and mix.
7. Add heavy cream (liquid), milk into a small bowl and microwave for about 40 sec at 600w to reach about 40℃. Then add into the egg yolk mixture, and mix. Finally add yogurt, mix well them again. Set aside.
8. Place the egg whites in a large clean bowl (or the stand mixer), use an electric mixer to beat them, adding rest of the sugar (40g) graduately until SOFT peaks.
9. Add the egg white in 3 times. Take about 1/3 of the egg whites and fold them into the egg yolk mixture, mix well. Add another 1/3 of the egg whites and mix lightly. Finally add the remaining egg whites and mix gently using spatula until the batter is evenly combined.
10. Pour the mixture into the cake pan. Tap the bottom of the cake pan a few times to release any air pockets in the mixture. Remove any bubble on surface with a chopstick.
11. In a oven-safe pan, place folded cloth and place the cake mold. Add the warm water (about 40℃) and bake in the oven (without fan) preheated at 150C° for 1h. Then another 5 mins at 160C°. Turn off the oven and open the oven door comletely for about 1 to 1.5 min to cool the temperature. Close the door and let leave the cake in the oven for about 1h. This should prevent the cake from shrinking too much.
12. Remove the cake pan from the oven.
13. Let the cake cool for 10 min at room temperature, then unmold. You can enjoy the cake immediately or chill in the refrigerator before serving. You can store it in the fridge for up to 3-4 days.