This dessert is an impressive crowd-pleaser – and it definitely takes some time and some skill to prepare.
The flavors are dark and decadent – bittersweet chocolate, the bite of toasted walnuts and the sweet tang of homemade caramel.
Walnut Crust
1 large egg, separated
1/4 t vanilla extract
1/2 c toasted walnuts – see note in recipe regarding toasting walnuts
1/2 c powdered sugar
1 c flour
pinch of table salt
5 T cold unsalted butter, cut into 1/2-inch cubes
Caramel-Walnut Filling and Garnish
1/4 c water
1 c granulated sugar
2/3 c heavy cream
3 T unsalted butter, cut into 3 pieces
1/2 t vanilla extract
1/2 t lemon juice
pinch table salt
16 – 18 toasted walnut halves, plus 1 c toasted walnuts, coarsely chopped – see note in recipe regarding toasting walnuts
Chocolate Filling
2 large egg yolks
1 T plus 1/3 c heavy cream
1/3 c whole milk
5 oz semisweet chocolate, chopped fine
2 T unsalted butter, cut into 4 pieces
Toasting the walnuts: All the nuts in this recipe must be toasted to bring out their full flavor. Put them all together on a baking sheet in a 375-degree oven for 8 – 10 minutes until they’re fragrant and light brown.
For the crust: Process nuts and sugar in Cuisinart until finely ground, 8 to 10 seconds. Add flour and salt and pulse to combine. Scatter butter and pulse to cut butter in to resemble coarse meal.
Beat egg white til frothy. Remove 1 T of egg white to a second bowl and add yolk and vanilla (reserve the remaining egg white for later). With Cuisinart running, add egg yolk mixture to sugar – nut mixture until a ball forms. Form into a thick 6 -inch disc, wrap in plastic and refrigerate 30 minutes.
Roll out dough between 2 sheets of wax paper to a 13-inch round. Slip onto a baking sheet and freeze for 15 minutes. Spray 9 – inch tart pan with removable bottom with non-stick cooking spray.
Remove dough from freezer and discard top sheet of wax paper. Invert tart pan over dough (removable bottom will fall onto dough) and press down to cut through the dough. Placing one hand on tart pan bottom and one hand underneath baking sheet, carefully flip everything over and place on counter. Peel wax paper off dough and use a rolling pin, if necessary, to completely slice through dough around the edges of tart pan. Put the tart pan aside, and in a few minutes the dough will gently slide down into the bottom of the pan. Gently ease and press it down, if necessary. To form the sides of the crust, roll the scraps into ropes and press into the flutes of the pan. Sides should be 1/4 inch thick.
Freeze the dough-lined tart pan at least 30 minutes – and if it’s tightly wrapped, it can be frozen up to 1 month.
{30 minutes to make the dough, 30 minutes to chill it (while you tidy & prep caramel & chocolate) and 10-15 minutes to shape the dough into the pan}
Heat oven to 375 and line chilled dough with foil, then pie weights. Make sure they go all the way up the sides, otherwise the crust will pull away from the tart pan. Bake 30 minutes, rotating halfway through. Watch it to be sure it doesn’t begin to burn. Remove the foil and weights and bake another 5 minutes. Cool on baking rack 5 minutes, then brush hot crust with the reserved egg white. Reduce oven to 300 degrees.
Put the crust back onto a cool baking sheet, to make it easier to move in and out of the refrigerator without dislodging the bottom of the pan prematurely.
For filling and garnish: Put water in a heavy-bottomed pot. Add sugar to the center, being carefully no sugar touches the edge of the pot. Boil, covered, over medium-high heat, swirling once or twice to dissolve sugar. Uncover and continue to boil, without stirring, until sugar is a deep amber, begins to smoke, and registers about 375 degrees on an instant-read thermometer, 5 to 10 minutes. Remove pan from heat.
Carefully add half the cream – mixture will sputter and steam. Add remaining cream and let bubbling subside. Return pan to low heat and stir til smooth. Add butter and stir to melt. Remove pan from heat, add vanilla, lemon juice and salt.
Add the walnut halves to the caramel mixture and stir to coat. Allow caramel to set, about 8 minutes. Put a cooling rack over a piece of foil and set the pot of caramel next to it. With a fork, fish the walnut halves out of the caramel, let the excess caramel drip off, and then carefully put them down on the baking rack.
Stir chopped toasted walnuts into the caramel, then pour evenly into the tart shell. Refrigerate, uncovered (on a baking sheet), until caramel is set and doesn’t move when the pan is tilted – about 20 minutes.
{20 minutes: Make the caramel & coat the walnuts}
Chocolate filling. Whisk yolks and 1 T cream in a small bowl. Bring milk and remaining 1/3 c cream to simmer in small saucepan. Off heat, add chocolate and butter. Cover the pan and let stand until chocolate is mostly melted, about 2 minutes. Stir until smooth, then add yolk mixture. Pour the filling into the caramel-filled tart shell, tilting the pan if necessary to distribute chocolate evenly.
{25 minutes: Make the chocolate filling}
Bake at 300 degrees on baking sheet about 25 minutes. The chocolate layer should be set, and small bubbles will appear – but the filling will be wobbly because the caramel layer is warm.
Arrange the caramel-coated walnut halves on the surface of the tart, around the perimeter. Cool about 30 minutes, then refrigerate at least 3 hours or up to 24 hours.