1 cup unsated butter
16 ounces bittersweet chocolate chips
1/4 teaspoon salt
Preheat oven to 350°F. Grease springform pan with butter and line bottom with parchment.
Using an electric mixer on high speed, beat eggs in a large bowl until doubled in size, about 5 minutes.
Place chocolate chips, salt, and 1 cup butter in a large microwave-proof bowl. Microwave on high in 10-second bursts, stirring between bursts, until smooth and pourable.
Using a rubber spatula, gently fold one-third of the whipped eggs into chocolate mixture until incorporated. Fold egg and chocolate mixture back into remaining whipped eggs until incorporated.
Transfer to prepared pan; cover bottom and sides of pan completely with foil. Set springform pan inside a large roasting pan; add hot water to a depth of about 1″.
Bake cake until a toothpick inserted into the center comes out clean and sides of cake begin to pull away from pan, 30–40 minutes. Let cool before serving.
I got the recipe here.