Position a rack in the center of the oven and preheat it to 350F. Line the bottom and sides of an 8 by 8-inch baking pan with parchment paper.

In a large heatproof bowl that fits over a large pot to make a double boiler, combine the cocoa powder, 1 bar (4 ounces / 113g) of the chocolate, the butter, and sugar. Set the pot over medium heat and add a few inches of

water. Bring the water to an aggressive simmer, set the bowl over the top, and stir constantly to melt everything together. You'll want to be on top of it, since this will take some time, and you don't want the chocolate or sugar to burn.

In a medium bowl to the side, whisk together the egg, creme fraiche, and orange juice.

When the chocolate mixture has fully melted, stir for another 30 seconds or so before moving the pot to the counter. If you taste it at this point, the sugar should still taste grainy. Let this cool for a few minutes to go from

hot to warm.

Gradually drizzle the egg mixture into the chocolate mixture, whisking constantly. The batter should still be warm when you mix in the flour, 1 teaspoon salt, and the orange zest. Chop the remaining ½ bar (2 ounces /

57g) of chocolate and mix it into the warm batter; it's okay if it melts a bit.

Pour the batter into the lined baking pan and bake until the top of the brownies is shiny and cracked and you can insert a toothpick and it comes out clean, 25 to 30 minutes.

Smack the pan on the counter a few times after baking to ease it into its wrinkly top. Let cool on the counter for 30 minutes or until the pan is cool to the touch, then transfer the pan to the fridge and let cool for another 45 minutes, or until the bottom of the pan is completely cold. This chilling is what gives the brownie its signature truffle-y chew.

Slice and serve.