Step 1: Prepare the Crust

1. Crush the Biscuits: Start by crushing the digestive biscuits or graham crackers. You can use a food processor for a fine texture, or place the biscuits in a ziplock bag and crush them with a rolling pin until you get fine crumbs.

2. Mix the Crust: In a mixing bowl, combine the crushed biscuits with the melted butter and sugar. Stir until the mixture is evenly combined and resembles wet sand.

3. Press the Crust: Transfer the biscuit mixture to a 9-inch (23 cm) springform pan or pie dish. Press the crumbs down with the back of a spoon to create an even layer at the bottom. Be sure to press it firmly so it holds together when the cheesecake is set.

4. Chill the Crust: Place the crust in the fridge to chill while you prepare the cheesecake filling. This will allow the crust to firm up and set.

Step 2: Prepare the Cheesecake Filling

5. Bloom the Gelatin: In a small bowl, sprinkle the gelatin powder over 2 tablespoons of cold water. Let it sit for about 5 minutes to bloom. The gelatin will absorb the water and swell up, preparing it for the next step.

6. Dissolve the Gelatin: After the gelatin has bloomed, gently heat it in the microwave for 10-15 seconds or on the stovetop until it becomes liquid. Stir to ensure there are no lumps. Let it cool slightly.

7. Whip the Cream: In a separate large bowl, whip the heavy cream with a hand mixer or stand mixer until stiff peaks form. Set aside.

8. Mix the Cream Cheese: In another bowl, beat the softened cream cheese with a hand mixer until smooth and creamy. Add the powdered sugar, vanilla extract, lemon juice, and lemon zest. Continue to beat until well combined.

9. Combine the Gelatin and Cream Cheese: Slowly add the dissolved gelatin into the cream cheese mixture, mixing until incorporated. Make sure the gelatin isn’t too hot when you add it, as it could cause the mixture to curdle.

10. Fold in the Whipped Cream: Gently fold the whipped cream into the cream cheese mixture. Use a spatula to mix, being careful not to deflate the whipped cream. This will keep the filling light and airy.

Step 3: Assemble the Cheesecake

11. Fill the Pan: Pour the cream cheese filling over the chilled crust, smoothing it out with a spatula. Make sure the filling is evenly distributed and there are no air bubbles.

12. Chill the Cheesecake: Cover the cheesecake with plastic wrap or foil and refrigerate for at least 3-4 hours, or preferably overnight. This will allow the cheesecake to set properly.

Step 4: Prepare the Lemon Jelly Topping

13. Prepare the Jelly: In a small saucepan, heat the water and sugar (if using) over low heat until the sugar dissolves. Once the sugar has dissolved, stir in the lemon-flavored gelatin. Bring the mixture to a boil, then remove it from the heat and let it cool to room temperature.

14. Top the Cheesecake: Once the cheesecake filling has set, carefully pour the cooled lemon jelly over the top. Ensure that the jelly layer is evenly spread across the surface.

15. Chill Again: Return the cheesecake to the refrigerator and chill for another 1-2 hours, or until the jelly has fully set and the cheesecake is firm.

Step 5: Garnish and Serve

16. Garnish the Cheesecake: Once the cheesecake has set, remove it from the fridge and carefully run a knife around the edge of the springform pan to release the sides. Top the cheesecake with fresh mint leaves, lemon slices, or a dollop of whipped cream for an extra touch of elegance.

17. Slice and Enjoy: Cut the cheesecake into slices and serve chilled. The cheesecake should have a creamy filling with a smooth, glossy jelly topping.