"An amazing French fondant. It's easy to make, but looks and tastes like you are a professional chef. The quality of chocolate is the most important factor to the success of this recipe. Make sure you don't overcook it, because it is essential that the center remains wobbly. You will impress people with it for sure."
Place chocolate and 1 cup plus 1 1/2 tablespoons butter in top of a double boiler over simmering water. Stir frequently, scraping down the sides with a rubber spatula to avoid scorching, until melted, about 5 minutes.
Beat eggs, vanilla, and salt together in a bowl using an electric mixer until creamy. Add sugar; blend well. Stir in chocolate-butter mixture with a spoon. Add flour, about 2 tablespoons at a time, mixing well after each addition until fondant mixture is smooth.
Butter a 9-inch round pan. Pour the fondant mixture evenly into the pan; cover with aluminum foil. Freeze until firm, 4 hours to overnight.
Preheat oven to 356 degrees F (180 degrees C).
Bake the fondant in the preheated oven until sides are firm and center is still liquid, about 40 minutes.