In a medium bowl, combine the egg whites and sugar and beat with a whisk until light and fluffy, 3 to 5 minutes. Stir in the flour, salt, melted butter, heavy cream and vanilla with a rubber spatula until combined.
Prop up each end of a long wooden spoon on a can or bowl (you'll use this to shape the taco shells). Heat a large nonstick pan over medium-high heat; coat with cooking spray. Spoon 2 tablespoons of batter into the pan; use a small offset spatula to spread the batter into an even 4- to 5-inch pancake. Cook on the first side until golden brown at the edges, 2 to 3 minutes. Flip and cook until golden brown on the reverse side, about 1 more minute. Remove from the pan and immediately drape the pancake over the wooden spoon. Set aside to set, about 5 minutes. Repeat to make 8 to 10 tacos, wiping out the skillet and adding more cooking spray as needed.
Put the chocolate chips in a heatproof bowl set over a saucepan of simmering water; stir until melted. Dip the edges of the taco shells in the melted chocolate and return to the wooden spoon; let set, about 5 minutes. (If making in advance, refrigerate until ready to serve.) Fill the taco shells with ice cream and garnish with some chopped pecans.
Photograph by Ryan Dausch
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.