Preheat oven to 325°F (163°C). Line the base of a 9-inch springform pan with parchment paper.
Mix crushed digestive biscuits and melted butter in a bowl. Press the mixture into the base of the pan to form an even crust.
Bake the crust for 10 minutes. Remove and let it cool completely.
In a large mixing bowl, beat softened cream cheese and caster sugar until smooth.
Add lemon curd, baking powder, and whipping cream. Beat again until fully combined.
In a separate bowl, beat the egg whites until soft peaks form. Gently fold into the cream cheese mixture.
Puree blueberries and stir into the filling. Add food coloring for a deeper gothic color if desired.
Pour the filling over the cooled crust and smooth the top with a spatula.
Bake for 50–60 minutes until the center is slightly jiggly but the edges are set.
Turn off the oven, crack the door open, and let the cheesecake cool for 1 hour inside the oven.
Transfer the cheesecake to the refrigerator and chill for at least 2 hours.
Once fully chilled, remove from the pan and top with extra blueberries, icing sugar, or whipped cream before serving.