1) Preheat oven to 160C/Gas 2. Butter a circular pie plate.
2) Melt chocolate and butter in an iron skillet over medium heat; stir to prevent scorching. Remove from heat when melted. Whisk in sugar, vanilla, flour, and salt.
3) In a small bowl, whisk the eggs together and add a little hot brownie mixture. This will temper the eggs and not cook them, when they go into the skillet. Pour eggs into skillet along with the pecans. Mix well. Pour into prepared pie plate.
4) Bake in the preheated oven for 40 minutes. Let cool and frost.
5) Cut into squares, top with whipped cream or ice cream and serve.
For the marshmallow cream frosting:
1) Beat all the ingredients together in a large bowl until well combined.