Chocolate torte recipes
I've made this recipe wheat-free.org/wheat-gluten-free-chocolate-torte-royale-recipe.html several times, it's very popular with people who can't eat wheat as well as people who can.
It uses ground almonds instead of hazelnuts though, and has a few more ingredients than those you listed so it may not be suitable after all if they are rigid on just the three ingredients you listed. But it is amazingly tasteful and moist in the centre, with a slightly crunchy texture on the outside, a bit likeperfect chocolate brownies should be.
Or for a cold cake, which works well for all occasions and doesn't need additional frosting, you could try this wheat-free.org/wheat-gluten-free-chocolate-torte.html If I come up with a recipe in my archive for just hazelnuts, eggs whites and chocolate I'll post it asap.
Helen