Milky Way Tart

Instructions

Make the mousse

Place the chocolate in a small heatproof bowl. In a medium saucepan, combine the cream and instant coffee powder and heat over medium-high heat until the mixture is scalded, which is when bubbles start to form around the edge of the pan but the cream isn't boiling.

Immediately pour the hot cream mixture over the chocolate and let stand for about 1 minute. Whisk gently until the chocolate is completely melted and the mixture is smooth.

Strain through a fine-mesh sieve into a small container, stir in the salt, cover tightly, and refrigerate until it's absolutely, completely chilled, at least 8 hours and up to 3 days. A few hours is not enough. (Because the cream has been heated, it will not whip properly unless it is very cold.)

Make the caramel filling

Place the sugar in the bottom of a medium saucepan and slowly pour in the water. Stir gently to moisten the sugar. If any sugar crystals are clinging to the sides of the pan, brush them down with a pastry brush dipped in water. Place the pan over medium-high heat and leave it undisturbed until the mixture comes to a rolling boil. (You want to avoid crystallization of the syrup, which can happen if the pan is disturbed before the sugar starts to color.) Then continue to boil rapidly without moving the pan until the sugar syrup starts to caramelize. This will take 3 to 4 minutes: the sugar syrup will boil furiously; then as it thickens, it will boil more languidly; and then you will see some of the syrup starting to color and darken around the edge of the pan.

When you see color in the pan, gently swirl it in a circular motion so the sugar caramelizes evenly. The syrup will start to turn golden brown, and then as you swirl the pan, the syrup will continue to get a bit darker and then darker still. To check the true color of the caramel, tilt the pan so you can see the syrup covering the bottom. This is the actual color of the caramel, and you want to keep cooking the caramel until this layer is a deep amber-brown. It takes just seconds for caramel to go from great to burnt, so be sure to tilt and check constantly.

As soon as the caramel is ready, slowly add the cream and then reduce the heat to low. Be careful. The steam that rises when the cream hits the caramel is extremely hot. Let the caramel and cream sputter for a few seconds until the mixture settles down, and then whisk to mix in the cream. Turn the heat up to medium and whisk together the caramel and cream (the mixture will have hardened a bit) for 2 to 3 minutes, or until they come together. Whisk in the butter, salt, and vanilla. Remove from the heat, pour into an airtight heatproof container, and refrigerate for at least 4 hours and up to 1 week.

Assemble the tart

Place the tart shell on a flat plate. Spread about 3/4 of the caramel filling evenly in the bottom of the tart shell.  TESTER TIP: You'll need to let the caramel warm slightly to room temperature before it'll be ready to spread. Or you can simply microwave it at 50% power for about 15 seconds.

Using a stand mixer fitted with the whip attachment, a hand-held mixer or a whisk, beat the mousse on medium speed until it holds soft peaks. Mound the mousse in the tart shell, and spread it evenly over the caramel filling. Drizzle the remaining 1/4 caramel filling in a crisscross pattern on top of the mousse. Using the back of a small knife or a vegetable peeler, shave curls from the milk chocolate slab. (Make sure the chocolate is slightly warm, or you'll end up with splinters instead of curls.) Decorate the tart with the curls. 

Refrigerate the tart for at least 30 minutes before serving. (The tart can be stored in an airtight container in the refrigerator for up to 8 hours.)

Dessert