Flourless Almond Cookies and the Science of Deduction

Let's play a game.
Let's play murder.

?! I'm sorry, did I say murder? I meant to say cookies! Yes, cookies.
Imagine you have a list of ingredients for these absolutely brilliant cookies, but without specifications of quantities or method to make them. What would you do?

"Egg whites, sugar, almonds, walnuts, hazelnuts." Their consistency is far from meringue, more like... macaroons! But more flaky than macaroons, much more flaky, and also quite soft. Put more ground nuts than the usual macaroon recipe and more sugar in the batter!

Batch 1 results: Batter too soft to handle with hands, cookies come out too dry with a consistency of a nutty meringue... not good. More nuts next time.
Batch 2 results: Still too dry, not good. Not good at all. What next? More almonds? more sugar?? Maybe there's something else that's not listed in the ingredients?? why aren't they soft?!

Narrow it down!
Whites, sugar, nuts...

Narrow - It - Down!
Whites, sugar, nuts... What am I missing?

Look at these cookies! Rough grain inside and easily visible on the surface... Covered with flaked almonds. Entirely.
Entirely covered with flaked almonds! bottom too! I hadn't observed that before. Who would go the lengths of covering it entirely with flaked almonds when the batter is so soft?! too soft to handle or roll in your hands? That would be a nightma... Oooh! That's because it isn't! It is not supposed to be soft at all.

Which suggests?
... I need to add more ground nuts, loads, loads more.

Bingo!

Off topic: or rather, sort of on topic - do yourselves a favor and go watch the adventures of Sherlock Holmes and John Watson in the BBC's Sherlock, this show is utterly brilliant!
And while you are at it, go do yourselves an even bigger favor and read the books!

These cookies have no flour in them, whatsoever. They are just perfect for Passover!

Flourless Almond Cookies

makes about 30 cookies

Ingredients:
2 egg whites
200g granulated sugar
70g walnuts
70g hazelnuts
140g almond meal*
zest of 1/2 a lemon
about 1/2 a cup of flaked almonds

Method:
Whisk the egg whites with a pinch of salt using an electric mixer. As white foam starts to form, gradually add in 50g of sugar. Whisk until firm peaks form, that is the peaks are firm but the very tip folds back on itself when you turn the whisk upside down.

Grind the walnuts and hazelnuts in a food processor. Add the almond meal, lemon zest and remaining 150g of sugar and stir till the mixture is fairly uniform. Fold in the egg whites. The mixture will become a sticky dough at this point.

Preheat the oven to 190 degrees Celsius.
Make cookies using a teaspoon or a cookie scoop (mine says it holds 1 tablespoon, but I don't believe it) and roll each cookie in flaked almonds. Bake for about 13 minutes, until they just barely start to golden.

*Basically, it's just ground almonds. You want them to be not too fine but not too coarse. You can also use almond flour, which is about the same thing only without the skins.