Preheat the oven to 325°F (160°C). You will need at least 2.5in (6cm) deep 8in (20sm) springform pan. Cut 3.5-inch (9cm)-wide long strip and 8-inch (20cm) round circle of parchment paper. Line the sides and the bottom of the springform pan with the prepare parchment paper. Set aside.
Separate the egg whites and yolks. Set aside.
Place the chocolate pieces in a medium heatproof bowl. Set the bowl over simmering water and slowly melt the chocolate. Add the cream cheese and mix until the mixture is smooth.
Remove from heat and cool slightly, for 2-3 minutes. Stir in the egg yolks.
In a large mixing bowl with whisk attachment, or using handheld electric mixer, beat the egg whites until hard peaks form. Add 1/3 of egg whites and stir into the chocolate mixture, until combined. Then gently fold in the remaining egg whites until the mixture is well-combined, no white streaks are visible.
Transfer the batter into the prepared pan and tap on the counter a few times to release any air bubbles. Place a baking sheet on the lower rack of the oven and pour about 2 cups of boiling water. Put the cake pan on the middle rack above the rack with water bath. Bake for 45 minutes. Turn off the oven and cool the cake in the oven for 30-40 minutes. Remove the sides of the springform pan and gently peel off the parchment paper from the sides. Cool completely on the counter, then refrigerate until ready to serve. Before serving, when the cake is chilled and set, gently remove the parchment paper on the bottom and place the cake on the platter. Dust some powdered sugar, if desired.