Step 1

Lightly sprinkle the inside of a 8½-by-4½-inch loaf pan with water. Line the pan with a 15-inch sheet of plastic wrap placed lengthwise in the pan. Press the plastic against the bottom, into the corners and up the sides of the pan so it lies flush against the surface; the water should help the plastic adhere. Smooth any wrinkles as best you can; allow the excess to overhang the edges of the pan.

Step 2

In a medium saucepan over medium, bring about 1 inch of water to a simmer. In a large heatproof bowl, combine the chocolate and butter. Set the bowl on top of the saucepan; be sure the bottom does not touch the water. Stir often until the chocolate and butter are melted. Remove the bowl from the pan, then stir in the cardamon and salt; set aside. Reserve the saucepan and water.

Step 3

In a stand mixer bowl, whisk together the coffee, sugar and egg yolks. Return the water in the saucepan to a bare simmer. Set the mixer bowl on the saucepan; make sure the bottom does not touch the water. Whisk constantly until the mixture is foamy, mounds softly when the whisk is lifted and reaches 145°F to 150°F, 4 to 5 minutes.

Step 4

Remove the bowl from the pan and attach it to the mixer along with the whisk attachment. Begin whipping, gradually increasing to high, and whip until the mixture is voluminous and holds peaks when the whisk is lifted, about 2 minutes; it may still be warm to the touch. Remove the bowl from the mixer. Gently scoop about half of the yolk mixture into the chocolate and fold with a silicone spatula until almost fully combined. Add the remaining yolk mixture and once again fold until almost fully combined (it’s fine if the mixture is streaky); the yolk mixture will deflate slightly.

Step 5

In the same mixer bowl using the whisk attachment (no need to wash the bowl and attachment), whip the cream on medium-high until it holds medium peaks, 1 to 2 minutes. Remove the bowl from the mixer. Add about one-third of the whipped cream to the yolk-chocolate mixture and fold until a few streaks remain. Scrape in the remaining cream and fold until well combined and no streaks remain. Pour into the prepared pan, then spread to the edges and smooth the top. Cover with another sheet of plastic wrap laid directly against the surface. Refrigerate for at least 6 hours or up to 3 days.

Step 6

When ready to serve, have ready a glassful of hot water and a small icing spatula. Peel off the plastic wrap covering the terrine. Make sure the plastic overhang is pulled to the sides and not covering the surface. Invert a serving platter onto the loaf pan and, holding the two together, carefully re-invert. Lift off the pan, tugging at the plastic wrap, if needed, to unmold the terrine. Remove and discard the plastic wrap. Dip the icing spatula into the hot water and allow to warm for a few seconds, then wipe dry. Smooth the sides of the terrine with the spatula, reheating and wiping the blade as needed.

Step 7

Spoon some cocoa into a fine-mesh sieve and dust the surface of the terrine. If desired, use a vegetable peeler to shave the chocolate bar (begin shaving at an edge) over the terrine, allowing the curls and shavings to fall onto the surface, until covered to your liking. Serve chilled.