Prepare the Whipped Cream:

1. Whip the Cream: In a mixing bowl, beat the heavy cream with powdered sugar and vanilla extract until stiff peaks form. Set aside in the refrigerator to keep it cool.

Prepare the Chocolate Hazelnut Layer:

2. Combine Hazelnut Spread and Milk: In a separate bowl, whisk together the chocolate hazelnut spread and milk until smooth and well combined. This mixture will serve as one of the dessert layers.

Prepare the Ganache:

3. Prepare the Chocolate Ganache: If using homemade ganache, heat 1 cup of heavy cream until warm (not boiling), then pour it over 1 cup of chopped dark chocolate. Stir until smooth. If using store-bought ganache, just warm it slightly in the microwave.

Assemble the Trifle:

4. Layer the Trifle: In a large glass trifle dish or individual serving cups, begin by layering the chocolate hazelnut mixture at the bottom. Follow with a layer of whipped cream, and then sprinkle with the chopped Ferrero Rocher chocolates. Repeat this process until the trifle is filled, finishing with a layer of whipped cream on top.
5. Add the Ganache: Pour the chocolate ganache over the top layer of whipped cream. This will create a glossy, rich topping that will soak into the layers slightly.

Chill and Serve:

6. Refrigerate: Place the trifle in the refrigerator for at least 2-3 hours (or overnight) to allow the flavors to meld together and the dessert to firm up.
7. Garnish and Serve: Before serving, garnish the trifle with crushed hazelnuts, extra Ferrero Rocher chocolates, or cocoa powder for a finishing touch.