1/2 cup (1 stick) unsalted butter, cut into 1″ pieces, plus more, room temperature, for pan
3/4 cup plus 2 tablespoons sugar, divided, plus more for pan
10 ounces semisweet or bittersweet chocolate (61%-72% cacao), coarsely chopped
2 tablespoons vegetable oil
6 large eggs
2 tablespoons natural unsweetened cocoa powder
1 teaspoon vanilla extract
3/4 teaspoon kosher salt
1 cup heavy cream
1/2 cup mascarpone
3 tablespoons powdered sugar
Preheat oven to 350°F. Lightly butter springform pan and dust with sugar, tapping out any excess.
Combine chocolate, oil, and 1/2 cup butter in a large heatproof bowl. Set over a saucepan of simmering water and heat, stirring often, until melted. Remove bowl from saucepan.
Separate 4 eggs, placing whites and yolks in separate medium bowls. Add cocoa powder, vanilla, salt, 1/4 cup sugar, and remaining 2 eggs to bowl with yolks and whisk until mixture is smooth. Gradually whisk yolk mixture into chocolate mixture, blending well.
Using an electric mixer on high speed, beat egg whites until frothy. With mixer running, gradually beat in 1/2 cup sugar; beat until firm peaks form.
Gently fold egg whites into chocolate mixture in 2 additions, folding just until incorporated between additions. Scrape batter into prepared pan; smooth top and sprinkle with remaining 2 tablespoons sugar.
Bake until top is puffed and starting to crack and cake is pulling away from edge of pan, 35-45 minutes. Transfer to a wire rack and let cake cool completely in pan (cake will collapse in the center and crack further as it cools).
For whipped cream:
Add heavy cream, mascarpone and powdered sugar to whipped cream dispenser. Charge with 1 N20 cream charger and put on top of cake.