Toast the walnuts on a baking sheet in the preheated oven for 8 to 10 minutes. Cool to room temperature.
Process the walnuts in the bowl of a food processor fitted with a metal blade until finely chopped, about 8 to 10 seconds.
Heat the granulated sugar, water and corn syrup in a 3-quart saucepan over medium-high heat, stirring to dissolve the sugar. Bring to a boil. Continue to boil, stirring often, until the temperature of the syrup reaches 250 degrees Fahrenheit, about 5 minutes.
As soon as the syrup begins boiling, place the egg whites in the bowl of an electric mixer fitted with a balloon whip. Whisk on high speed until soft peaks form, about 4 minutes. Change the mixer speed to medium. Carefully and slowly pour the 250 degree Fahrenheit syrup into the whisked egg whites and continue to whisk on medium until the meringue is very thick, about 4 minutes. Remove the bowl from the mixer. Working quickly, use a rubber spatula to fold the walnuts and then the chocolate morsels into the meringue creating a variegated mixture. Divide the mixture into 24 large heaping tablespoons onto a two large pieces of waxed paper, using a finger to push the mixture off the spoon onto the wax paper. Allow to cool to room temperature for about an hour before storing in a tightly sealed plastic container.