1/4cupunsalted butter, plus 1 tablespoon for buttering the pan
Pinch of kosher or coarse sea salt
Confectioners' sugar, optional
Lightly sweetened whipped cream, optional
Preheat oven to 350°F. Butter a 9-inch springform pan and line bottom with parchment paper.
Bring about 2-inches of water to a simmer in the bottom half of a double boiler or in a medium saucepan. Place the top half of the double boiler, or a metal bowl or heatproof pan if not using a double boiler, over the simmering water and melt together the chocolate and the 1/4 cup butter. Set aside to cool.
Using a blender, chop the pecans finely. Add the eggs, vanilla, sugar, salt and melted chocolate mixture, blending until smooth. Pour the batter into the buttered springform pan and bake until a toothpick inserted in center comes out moist but not wet, about 40 minutes.
Once it has cooled a little, run the tip of a knife around the pan and release the cake from the pan. Invert onto a plate, and then again, or serve directly onto plates if left on bottom part of springform pan. If desired, sprinkle with confectioners’ sugar and serve with whipped cream and berries.