In a food processor, pulse 250 g of the walnuts (about 2 full cups) for a few seconds until they resemble fine crumbs. Separately, roughly chop the other 50 g and reserve.

Heat a pot of water on the stove to a simmer

Put your egg whites in a metal bowl, place bowl over the simmering water and beat with a hand mixer until the egg white are frothy and almost stiff.

Reduce heat, and add the sugar gradually, a few tablespoons at a time, while continuing to beat. Add the finely ground walnuts, cinnamon, vanilla, and a pinch of salt, and beat over the water for another 5 minutes. Add the roughly chopped walnuts at this point.

Remove from heat, and let cool completely.

Preheat oven to 365° F (180° C), and line a couple of cookie sheets with parchment paper

Scoop about 2 tbs of the dough, and with wet fingers form small balls, about an inch in diameter. Slightly flatten them on top.

Bake for 10 minutes. Let dry.