Preheat oven to 350 degrees. Place hazelnuts in a single layer on a rimmed baking sheet; toast until skins begin to split, about 10 minutes. Rub warm nuts vigorously with a clean kitchen towel to remove skins. Return to baking sheet; toast until fragrant and golden brown, about 1 minute more. Cool; coarsely chop. Set aside.
In a small saucepan, combine sugar, water, and liqueur if using. Bring to a boil; stir until sugar has dissolved. Remove from heat; set aside to cool completely. Line a 9-by-5-inch domed metal or glass bowl with plastic wrap.
Cut rectangular sponge cake into thirds crosswise and lengthwise, making 9 rectangles. Reserve round sponge cake layer to use on top. Cut each rectangle diagonally in half, forming 18 triangles. Brush both sides of each triangle with some syrup. Line inside of bowl with triangle slices, pointed ends facing bottom of bowl, to form a sunburst pattern. Fit slices snugly so bowl is completely lined. Use small pieces of syrup-brushed cake to fill in gaps. Trim the cake top to make it even. Transfer lined bowl to refrigerator.
Place cream and confectioners' sugar in the bowl of an electric mixer fitted with the whisk attachment. Beat on medium until stiff, about 3 minutes. Gently fold in reserved nuts, toffee, and raspberries. Remove lined bowl from refrigerator, fill with cream mixture, and cover top with cake round. This will become bottom of zuccotto when unmolded. Cover with plastic wrap; refrigerate 12 hours or overnight.
Place a wire rack on top of bowl, and invert zuccotto onto rack. Place on a rimmed baking sheet. Remove bowl and plastic wrap. Using a ladle, pour ganache over top of dome, letting excess drip down sides onto rack. Make sure to coat entire surface of the zuccotto. Cut into wedges. Ladle with creme anglaise. Serve immediately, garnished
with chopped toffee, nuts, and berries.