Lemon-Pistachio Crunch Cake

Whisk all ingredients in heavy medium saucepan to blend. Cook over medium-low heat until curd thickens and candy thermometer registers 170°F, stirring constantly, about 7 minutes (do not boil).

Pour curd into small bowl. Press plastic wrap onto surface. Chill at least 1 day and up to 3 days.

Place large sheet of foil on work surface; butter foil.

Combine sugar, butter, and 1/4 cup water in heavy medium saucepan. Stir over medium-low heat until sugar dissolves and butter melts, occasionally brushing down sides of pan with wet pastry brush. Increase heat to medium-high and boil until syrup is medium amber color, stirring constantly, about 12 minutes.

Remove from heat. Immediately add baking soda (mixture will foam up), then nuts and stir to blend well.

Spread nut mixture onto prepared foil, separating nuts. Cool completely. Chop crunch into 1/4- to 1/3-inch pieces. (Can be made 2 days ahead. Store airtight at room temperature.)

Bring 3/4 cup cream to simmer in heavy medium saucepan.

Remove from heat.

Add chocolate and salt; stir until smooth.

Transfer frosting base to bowl. Cover; chill overnight.

Preheat oven to 350°F. Butter and flour three 9-inch-diameter cake pans with 1 1/2-inch-high sides. Sift flour, baking powder, and salt into medium bowl. Using electric mixer, beat butter in large bowl until fluffy. Gradually add 1 3/4 cups sugar, beating until well blended. Beat in vanilla and lemon peel. Beat in flour mixture alternately with milk in 3 additions each. Using clean dry beaters, beat egg whites in another large bowl until soft peaks form. Gradually add remaining 1/4 cup sugar, beating until stiff but not dry. Fold whites into batter in 3 additions. Divide batter among prepared pans.

Bake cakes until golden and tester inserted into center comes out clean, about 30 minutes. Cool cakes in pans on racks 15 minutes.

Cut around pan sides and turn cakes out onto racks. Turn cakes right side up and cool completely. (Can be made 1 day ahead. Wrap in foil and store at room temperature.)

Using serrated knife, cut off mounded tops of cake layers to level.

Place 1 cake layer on platter, trimmed side up.

Spread with half of lemon curd. Top with second cake layer, trimmed side up.

Spread with remaining lemon curd. Top with third cake layer, trimmed side down.

Whisk remaining 1 3/4 cups chilled cream into frosting base to loosen. Using electric mixer, beat until frosting holds stiff peaks.

Spread frosting over top and sides of cake. Chill until frosting is firm, at least 3 hours. (Can be made 1 day ahead. Cover with cake dome; keep chilled.)

Press crunch lightly into frosting on sides and top edge of cake. (Can be prepared 1 hour ahead and refrigerated.)