Preparation

• 1 Preheat an oven to 350€F. Line a 9-inch round removable-bottom cake pan with parchment paper.
• 2 Prepare the molten chocolate cake batter according to the package instructions. Add the tangerine zest and fold gently to combine; do not overmix.
• 3 Pour the batter into the prepared pan. Bake until the center of the cake is firm to the touch and a toothpick inserted into the center comes out almost clean, with only a few crumbs clinging to it, 35 to 40 minutes. Transfer the pan to a wire rack and let cool for at least 20 minutes.
• 4 Meanwhile, in a saucepan over medium-high heat, combine the granulated sugar and water and bring to a boil, whisking to dissolve the sugar. Reduce the heat to medium-low so the syrup barely simmers. Add the tangerine segments and cook for 5 minutes. Using a slotted spoon, transfer the tangerine segments to a bowl. Increase the heat to medium-high and cook until the syrup is reduced by half, about 10 minutes. Remove the pan from the heat.
• 5 Remove the outer ring from the pan. Place a plate upside down on top of the cake and invert the pan and plate together. Lift off the pan's removable bottom and peel off the parchment. Place a serving platter upside down on top of the cake and invert again, then remove the first plate.
• 6 Dust the cake with confectioners' sugar. To facilitate slicing, dip a knife blade in hot water and wipe it dry before cutting each slice. Accompany each slice with some of the tangerine segments, a spoonful of the syrup and a dollop of whipped cream.