Steamed chocolate cake with whipped cream

Chocolate cake

• 4 eggs, separated
• 100 g sugar
• 125 g dark chocolate (50% cocoa), cut into pieces (2 cm)
• 125 g unsalted butter, cut into pieces, plus extra for greasing
• 100 g plain flour, plus extra for dusting
• 1 tsp baking powder (5 g)
• 600 g water

Whipped cream and chocolate ganache filling

• 315 g pouring (whipping) cream, chilled
• 80 g dark chocolate (50% cocoa), cut into pieces (2 cm)