Preheat oven to 325 degrees. Butter 4 eight ounce ramekins.
Place the melted butter and cocoa in a medium size bowl. Whisk to thoroughly combine. Whisk in the eggs,sugar,flour and vanilla. Stir in the pecans.
Line a baking pan big enough to hold the ramekins with a cloth towel. Place the ramekins on top of the towel. (The towel helps the ramekins to stay in place when you add the boiling water to the pan.)
Place boiled water ( don't use hot tap water, boil the water ) into the pan so it comes half way up the ramekins. Place the baking pan in the oven, bake for 45 minutes or until the pots have a crusted top and are soft in the middle. Remove from the oven, serve warm or cold with whipped cream or ice cream for a fudgy chocolate treat.