1. Preheat the oven to 350°F.
2. Melt the chocolate and butter in a double boiler.
3. Remove from heat. Add sugar, eggs, and salt.
4. Add flour and mix.
5. Pour into a mold and bake for 12 minutes.
6. Sprinkle with marshmallows and bake for another 2 minutes.
7. Let rest for 5 minutes in the turned-off oven.
8. Remove from the oven and let cool to room temperature. Refrigerate for 1 hour.
9. Remove from the refrigerator, unmold, cut into individual portions, and serve.