Beat egg whites, slowly add sugar until glossy soft peaks form
In another bowl, mix flour, mix-ins and zest
Gently fold meringue into dry ingredients to create thick batter
Spoon batter into a lined or sprayed loaf tin
Bake in a preheated oven at 180°C for 30 minutes
Cool slightly, then slice thin with a serrated knife
Bake again for 20-25 minutes until golden and crispy
Dip in melted chocolate if desired
