For the Chocolate Cookie Crust

• 250 g (about 2 cups) chocolate cookie crumbs
  (such as Oreo or other chocolate biscuits, finely crushed)
• 75 g (5 tbsp) unsalted butter, melted
• 2 tbsp granulated sugar
• 1 pinch salt (optional, to enhance the chocolate flavor)

For the Dark Chocolate Cheesecake Filling

• 600 g (about 21 oz) cream cheese, softened
• 150 g (¾ cup) granulated sugar
• 3 large eggs, at room temperature
• 200 g (7 oz) dark chocolate (60–70% cocoa), chopped and melted
• 120 ml (½ cup) sour cream, at room temperature
• 60 ml (¼ cup) heavy cream
• 2 tbsp unsweetened cocoa powder, sifted
• 1 tsp vanilla extract
• ¼ tsp salt

For the Raspberry Swirl or Layer

• 200 g (about 1½ cups) raspberries (fresh or frozen)
• 3 tbsp granulated sugar
• 1 tsp lemon juice
• 1 tsp cornstarch mixed with 1 tbsp water (to slightly thicken the sauce)

For the Optional Chocolate Ganache Topping

• 150 g (5 oz) dark chocolate, finely chopped
• 150 ml (⅔ cup) heavy cream

For Garnish (Optional but Beautiful)

• Fresh raspberries
• Dark chocolate shavings or curls
• A dusting of cocoa powder or powdered sugar