Preheat oven to 425 degrees. Line a 9-inch round cake pan with parchment paper. Place a large heatproof mixing bowl over simmering water, or on the top of a double boiler. Stir together chopped chocolate and butter, until melted. Remove from the heat. Place a mixing bowl over warm tap water. Add eggs and beat with an electric mixer, until light in color and tripled in volume, about 3 minutes at medium speed and then high speed for another 5 minutes. Gently fold half of the eggs into the chocolate mixture.

Then fold in espresso beans. Add the remaining eggs, folding gently, until a few streaks remain. Be careful not to overmix. Pour batter into the cake pan. Place cake pans in a bain marie (water bath). Place in the oven and bake for 5 minutes. Cover the cake pan with aluminum foil and bake, still in the bain marie, and additional 10 minutes. Set aside to cool on a rack for 45 minutes, then refrigerate for at least 6 hours, to overnight. Turn oven down to 350 degrees. On a baking sheet spread pecan halves. Toast until golden, about 10 - 15 minutes. Set aside to cool. To remove cake from pan, place the pan over a low burner for a moment or two. Run a sharp knife around the inside edge to loosen the cake. Invert onto a platter.

Whisk the crema or creme fraiche with the sugar and vanilla until peaks form. Pile the stiff cream on the chocolate cake. Then, using a spatula, spread it out to the edges to make a thick even layer of cream over the top, being careful not to drip the white cream onto the sides of the cake. Refrigerate for 10 minutes to set. Arrange pecan halves on top of the cream to form a circle around the outside edge. Dip your fingertips or a fork into the melted chocolate and drizzle over the center in a free-form pattern. Refrigerate until serving time. The finished cake can be held overnight.

In large bowl whisk together cream and buttermilk. Cover and set in a warm place (a gas oven with just the heat from the pilot light for example) for 8 hours. Place in refrigerator. Can be kept for up to a week.