Leave yoghurt for about 10 hours in a coffee filter. Put something underneath to collect whey. I used cheap Natural British yoghurt from Tesco. Each 1 cup weighted about 230g and 3 cups was about 700g. Then, I got 272 g of ”yoghurt cheese” out of 3 cups of natural yoghurt after overnight.

Preheat the oven to conventional 170C / fan 160C

Put 50g of butter in a microwave-safe container and heat with 600w (or Medium power) for about 1 mins and mix and leave another 1 min to completely melt. Or if you don’t wish to use a microwave, melt the butter in a pan. This base is optional, as you could omit this biscuit base to reduce further calories. But of course, it tastes nicer with it.

Crush digestive biscuits with a rolling pin and pour melted butter. Stir the mixture until it is evenly moistened.

Or if you have a food processor, blend the digestive biscuits and the melted butter in a food processor until the mixture looks like wet sand.

Mixed well and lay in a cake tin. Press the mixture into the bottom of the pan. You could omit this base part in order to reduce further calories. Leave it in the fridge to set.

In a clean bowl, put 40g of the soft butter. Mix the soft butter well until it becomes creamy. If you only have a cold hard butter, you could microwave with 600w about 20 seconds.

Add yoghurt cheese (step #1) and mix them very well. You can use either a whisk or a spatula. I think it does not matter which one you will use at this stage.

Separate the egg white in a different clean bowl and add egg yolks into the yoghurt cheese mix. Leave the bowl with egg white aside. We will use this egg white in the step #13. With "a large wooden spoon or a spatula" mix well the egg yolks and yoghurt cheese mix. Sometimes, scrape the bottom of the bowl and mix well.

Wash the lemon very well and grate the zest of the lemon over the yoghurt cheese mixture (step #10) and add lemon juice as well. Mix well until it becomes smooth.

Whisk the egg white which you left aside at the step #10 until it becomes meringue which creates peaks.

Use "a large wooden spoon or a spatula" and add 1/3 of the step #13 (meringue) into the step #11 (yoghurt cheese & egg yolks). Mix lightly in and mix lightly. Add another 1/3 and repeat twice and mix all meringue. Please never knead it nor taking air. Mix like holding them.

Pour the batter into the cake tin. Try to pour the last bit of the batter not to the centre but the side as they are slightly heavier dough which will prevent from raising. Drop the tin several times to get rid of air bubbles.

Boil the hot water in a kettle.

Bake it at 170 degrees for 90 mins with 2-3 cm of hot water in the baking tray. If your cake tin has a loose bottom, please put foil around the cake tin so that water doesn’t go into the cake tin. It needs to be baked with steam but we do not want water to go into to the tin.

After taking it out from the oven, cool it down in the tin. Remove from the tin after cooling down completely. Cover it with foil or clinging film and refrigerate it for at least 8 hours or overnight, preferably 24 hours.

Before serving, sprinkle icing sugar or serve with a fruit sauce.

Optional fruit sauce. Put 150g (frozen or fresh) of raspberries (or other fruit) and 25-30 g of sugar, and 10ml (about 2 tsp) of water into a microwave safe container. Heat about 3-4 mins with 600w (or Medium power). Take it out from the microwave oven, mix it well and sieve it. It becomes like a purée after sieve it.