Turn on to preheat the oven 320F/160C. For the bath, prepare a deep pan and start boiling enough water to fill it. Prepare a medium loaf baking pan. Cut a wide strip of parchment to line the bottom and larger sides of it with lightly greased parchment. If your loaf pan is non-stick, line its bottom only. Important! Make sure you have enough water to cover up to 2/3 of the baking pan.
Press kefir cheese through a sieve — Important! Do not skip it!
Combine yolks, sugar, flour, milk, lemon zest, and lemon juice with a whisk in a saucepan. Place it over low heat and cook constantly whisking until thick. Take it off heat and let cool down a little, whisking. Add softened butter, cheese, and vanilla extract. Combine well making sure all ingredients are uniformly distributed.
Whip a meringue, soft peaks.
Fold meringue into the cheese mixture in three steps until incorporated.
Transfer the batter into the lined medium loaf baking pan. Smooth the top.
Place the baking pan into a larger pan with hot water. Bake in the hot oven for 50 minutes to an hour.
To make sure your cheesecake doesn't collapse, let it cool down VERY SLOWLY! Turn off the heat, crack open the oven door, and keep the cheesecake inside for the next 30 minutes.
Take the baking pan with cheesecake out of hot water and leave to cool down at room temperature. Let it reach room temperature. It'll take a few hours.
Chill the pan with cheesecake in a fridge for a few hours. Flip the cheesecake on a plate upside down, and remove the parchment lining.
Make a chocolate glaze and cover the cheesecake. Refrigerate for up to 3 days.
I like this cake without the base, but it makes it more difficult to transfer and serve. The best way to slice it to portions is by using a string or a thread. The best way to add the base is to shape sweet pie crust (pâte brisée) to the size, bake it separately, and place it on top of the chilled cake before removing it from the mold.