Description
A flexible midnight-black cocoa sponge rolled around stabilized purple blueberry-vanilla mascarpone cream.
Ingredients
Scale
- 4 large eggs (200 g without shells), room temperature
- 3/4 cup (150 g) granulated sugar
- 1/4 tsp fine salt
- 1 tsp (5 ml) vanilla extract, for the sponge
- 2 tbsp (30 ml) hot coffee
- 2 tbsp (30 ml) neutral oil
- 1/2 cup (63 g) all-purpose flour
- 1/4 cup (21 g) black cocoa powder
- 2 tbsp (11 g) Dutch-process cocoa powder
- 1/2 tsp baking powder
- 6 oz (170 g) mascarpone, cold
- 1/2 cup (60 g) powdered sugar
- 2 tbsp (12 g) fine freeze-dried blueberry powder
- 1 tsp (5 ml) vanilla extract, for the filling
- 1 cup (240 ml) heavy cream, cold
- 1 small drop violet gel food color, optional
- 2 oz (57 g) dark chocolate, melted, for drizzle
Instructions
- Heat the oven to 350°F (175°C). Line a 10-by-15-inch (25-by-38 cm) jelly-roll pan with parchment.
- Whip eggs, sugar, and salt for 5-7 minutes, until thick and ribboning.
- Mix vanilla, coffee, and oil. Stir in a scoop of egg foam, then fold back into the main bowl.
- Sift flour, both cocoas, and baking powder over the foam in two additions and fold gently.
- Spread evenly and bake for 10-12 minutes, until the center springs back.
- Turn onto cocoa-dusted parchment, peel away the liner, and roll from a short end while hot. Cool completely.
- Whip mascarpone, powdered sugar, blueberry powder, vanilla, cream, and optional color to medium-firm peaks.
- Unroll gently, spread filling evenly, reroll, wrap, and chill for 3 hours.
- Trim, drizzle with melted chocolate, and cut into 10 slices.
Notes
Do not overbake the sponge, and make the first roll while it is hot. Keep the dairy cold for a stable purple filling.