Wash the strawberries and cut into pieces. Place the strawberries and 100 g of sugar in a pan over medium heat. Bring to a boil and let it simmer for 5-7 minutes, stirring regularly.

Take a bowl and place a sieve on top. Add the strawberry mixture and press it firmly with a spatula or spoon to leave the seeds and any unwanted bits behind, resulting in a smooth sauce. Let it cool.

Place the cream cheese, mascarpone, sugar, and vanilla sugar in a large bowl. Mix for 1 minute. Sift the cornstarch into the bowl and mix until combined. Set the mixer aside and use a spatula from now on. Add the eggs one by one to the bowl, folding them gently into the mixture.

Line a baking tin or springform pan with a sheet of baking paper. Pour in half of the cheesecake batter and spread the strawberry mixture over it (reserve a little for garnish and put it in a piping bag). Spread the rest of the cheesecake batter evenly over the strawberry mixture.

Pipe drops of the strawberry mixture onto the cheesecake and run a toothpick through them to create a marbled pattern.

Place the strawberry cheesecake in a preheated oven at 125°C (257°F) and bake for 55-60 minutes, or until the sides are set and the center still wobbles slightly. Turn off the oven and let the cheesecake sit in the oven for 1 hour. This prevents the cheesecake from sinking or cracking. Store the strawberry cheesecake covered in the refrigerator to set, preferably overnight.