Begin by setting your oven to 160°C (320°F) for conventional or 140°C (295°F) for fan-assisted modes. Prepare a springform pan (20cm/8") by inverting its base, lightly greasing it, placing a parchment square over, and securing it back in place; grease and line the side as well.
For the crust, coarsely crush the biscuits, then blitz in a food processor into fine crumbs. Mix in the melted butter until the mixture resembles wet sand. Press into the pan, using a flat-based cup to mold the crust along the base and nearly to the top of the sides.
To prepare the filling, beat cream cheese briefly on medium speed until smooth—no more than 20 seconds. Add flour and blend just until incorporated. Introduce vanilla, lemon zest, sour cream, and sugar, beating lightly to combine. Mix in eggs individually, ensuring each is fully integrated before adding the next, but avoid overbeating.
Pour the batter into the crust and bake for 55 minutes. The surface should have a light golden hue, minimal jiggle, and no cracks. Cool the cheesecake in the oven with the door ajar (approximately 8 inches) before chilling it for a minimum of 4 hours.
For the topping, combine diced strawberries, lemon juice (or water), sugar, and vanilla in a saucepan. Simmer over medium heat for 10 minutes until softened. Stir in a slurry of cornflour and water, cooking until thickened. Fold in the halved berries, letting them soften for one minute, then remove from heat and cool. Adjust the consistency with a small amount of water if necessary.
Spread the cooled strawberry topping evenly over the cheesecake, ensuring strawberry halves are face-down. Chill for at least two hours before slicing. Serve with extra sauce drizzled over each portion.