Preheat oven to 400 degrees F. Lightly grease and flour six 1- to 1 1/4-cup soufflé dishes or six 10-ounce custard cups. Place soufflé dishes or custard cups in a shallow baking pan and set pan aside. In a heavy small saucepan melt butter and semisweet chocolate over low heat, stirring constantly. Remove from heat and cool.
Meanwhile, prepare Praline Sauce, cover and keep warm until needed. In a heavy medium saucepan combine sugar, brown sugar and dark colored corn syrup. Stir in whipping cream. Cook over medium-high heat until boiling, stirring constantly to dissolve sugar. Reduce heat. Cook, uncovered, 10 minutes or until thickened, stirring occasionally. Makes 1 cup sauce
In a large mixing bowl beat eggs, egg yolks, sugar, and vanilla with an electric mixer on high speed about 5 minutes or until thick and lemon colored. Beat in cooled chocolate mixture on medium speed. Sift flour and cocoa over chocolate mixture; beat on low speed just until combined. Divide batter evenly into prepared dishes or cups.
Bake 10 minutes. Pull cakes out of oven. Using a small spatula or table knife, puncture top of each partially-baked cake and gently enlarge to make a dime-sized hole. Slowly spoon about 1 tablespoon Praline Sauce into center of each cake. Return cakes to oven. Bake 5 minutes more or until cakes feel firm at the edges.
Cool in dishes on a wire rack for 5 minutes. Using a small spatula or knife, loosen cake edges from sides of dish or cup and slip cake out upright onto individual dessert plates. Stir 1/3 cup toasted pecan halves into the remaining Praline Sauce. If necessary, stir 1 to 2 tablespoons hot water into remaining sauce to thin. Spoon warm Praline Sauce on top of cakes. Top with pecan halves and sweetened whipped cream. Serve immediately.