Preheat oven to 325 degrees. Grease, flour (use either gluten-free flour or corn startch) & line a 9" spring form cake pan.
Place a large pan of water in the bottom of the oven. (This will keep the cake moist while baking.)
In a heavy saucepan, melt:
11 oz. semi-sweet chocolate, chopped
9 Tbsp butter, unsalted
Whisk until melted. Cool slightly then add:
pinch of salt
5 eggs.
Transfer batter into prepared pan. Bake for 50 minutes or until cake is set but still has a 3" size patch at the center which looks jiggly.
Cool on wire rack. Chill.
Optional: Serve cake with whipped cream. (Heavy whipping cream whipped with 1/2 tsp pure vanilla extract and 1/2 Tbps powdered sugar.)