1
["Put a small roasting pan filled halfway with hot water in bottom third of oven (to provide moisture during baking). Position another oven rack in middle of oven, then preheat oven to 325u00b0F. Butter springform pan and line bottom with a round of parchment or wax paper. Butter paper.", "Melt butter (2 sticks) and chocolate together in a 2-quart heavy saucepan over low heat, stirring, then remove from heat. Beat together yolks, 1/3 cup sugar, and salt in a large bowl with an electric mixer at medium-high speed until thick enough to form a ribbon that takes 2 seconds to dissolve into mixture when beater is lifted, 6 to 8 minutes in a stand mixer or 10 to 14 minutes with a handheld. Stir warm chocolate mixture into yolk mixture until combined well.", "Beat whites in another large bowl with cleaned beaters at medium speed until they just hold soft peaks. Gradually add 1/3 cup sugar, beating until whites just hold stiff peaks. Stir one fourth of whites into chocolate mixture to lighten, then fold in remaining whites gently but thoroughly.", "Pour batter into springform pan and bake in middle of oven (do not place springform pan in hot water) until a wooden pick or skewer inserted in center comes out with crumbs adhering, about 1 hour (a crust will form and crack on top of cake as it bakes). Transfer to a rack and cool 10 minutes (cake will ""deflate"" as it cools).", "Run a thin knife carefully around edge of cake, then remove side of pan. Cool cake on bottom of pan 30 minutes. Invert a rack over cake and invert cake onto rack, then remove bottom of pan and carefully peel off paper. Invert a serving plate over cake, then invert cake onto plate.", "Remove zest from 2 oranges and trim any white pith from zest with a paring knife. Cut enough very thin strips of zest to measure 1/4 cup. Squeeze juice from all 3 oranges and pour through a fine-mesh sieve into a bowl. Measure out 1 cup juice and reserve remainder for another use.", "Cook remaining 1/2 cup sugar in a dry 1- to 2-quart heavy saucepan over moderate heat, undisturbed, until it begins to melt. Continue to cook, stirring occasionally with a fork, until sugar is melted into a deep golden caramel. Add zest and cook, stirring, until fragrant, about 15 seconds. Tilt pan and carefully pour in juice (caramel will harden and steam vigorously). Cook over moderately low heat, stirring, until caramel is dissolved, then cool sauce.", "Serve cake with orange caramel sauce."]
