Heat oven to 350º.  Lightly dust a clean work surface with cornstarch. Line a 9- x 13- inch baking dish with parchment paper, letting excess paper hang over edges.

Spread nuts on a rimmed baking sheet. Bake, stirring once halfway through, until fragrant and golden, 10 to 12 minutes. Transfer pan to a rack; let nuts cool completely.

Put egg whites and salt into the bowl of an electric mixer fitted with whisk; set aside.

In a heavy 4-quart saucepan with candy thermometer attached, heat sugar and honey over medium heat, stirring with a wooden spoon, until mixture begins to simmer and sugar is mostly dissolved, 12 to 14 minutes (mixture will be very thick, then begin to loosen and turn cloudy). Continue cooking, stirring occasionally, until candy thermometer reaches 280º degrees. Continue to cook mixture, stirring once or twice, until temperature reaches 315º. It will take the mixture about 15 minutes more to reach that temperature (the mixture will begin to foam and darken in color as temperature increases). 

Meanwhile, beat egg whites on medium speed until firm peaks form. Add confectioners sugar and continue to beat until fully incorporated, about 1 minute more. Turn off mixer, leaving bowl in place.

When sugar mixture reaches 315º, remove from heat; stir until temperature reduces to 300º, 1 to 2 minutes, then carefully remove candy thermometer. With mixer on medium speed, slowly pour sugar mixture down the side of the bowl (egg mixture will double in volume, then decrease); continue to beat until mixture is cooled to warm and begins to lighten in color, about 5 minutes. Add vanilla and zest; beat for 1 minute more, then, using a wooden spoon or heatproof spatula, fold in nuts (mixture will be very sticky). 

Turn out candy onto prepared work surface; dust hands with cornstarch. Knead for 5 to 6 turns, then transfer to prepared baking dish. Dust hands with more cornstarch, then press candy to flatten and fill pan. Put pan on wire rack and let candy cool completely, about 1 hour.

Using parchment paper overhang, lift out candy from pan; cut candy into pieces. Layer in a sealed container, between sheets of parchment paper and let stand overnight, with container sealed and at room temperature, to dry, at least 8 hours or overnight. Candy can be kept, layered between sheets of parchment paper, in a sealed container at room temperature, for up to 3 weeks.