Base:

1. Crush 250 g Oreo cookies in a food processor or blender until fine. If you don’t have one, place cookies in a zip-top bag and crush with a rolling pin.
2. Mix the crushed cookies with 60 g melted butter until evenly combined.
3. Press the mixture firmly into the bottom and slightly up the sides of a 9 x 3 inch (23 x 7 cm) pan. Make sure it’s packed evenly to form a stable crust.
4. Freeze briefly for about 10–15 minutes to help the base set while you prepare the filling.

Filling:

1. Whip 112 g heavy cream in a clean, dry bowl until soft peaks form. The cream should hold shape but still be smooth.
2. In a separate bowl, mix 225 g cream cheese with 225 g Nutella until completely smooth and lump-free.
3. Gently fold the whipped cream into the Nutella mixture, using a spatula and slow folding motions to keep it light and airy.
4. Spread the filling evenly over the chilled Oreo base. Smooth the top with a spatula for a clean finish.
5. Refrigerate for at least 6 hours, or overnight, to allow the tart to fully set.

Decoration:

1. Warm 150 g Nutella slightly until it is pourable but not hot.
2. Spread the Nutella evenly over the top of the chilled tart.
3. Chill briefly to let the topping set.
4. Slice and serve, optionally garnishing with crushed hazelnuts, chocolate shavings, or fresh berries.