How to Make It
In a food processor, pulse the flour with 1/2 cup of the nuts, the salt and pepper until the nuts are finely chopped. Add the butter and process until the mixture resembles fine meal. Add the water and process until the dough comes together. Shape the dough into an 8-inch log, wrap in plastic wrap and refrigerate until firm.
Preheat the oven to 375°. Line 2 baking sheets with parchment or wax paper. Finely chop the remaining 1/4 cup of macadamia nuts and mix with the Parmesan. Cut the log into scant 1/4-inch-thick slices and arrange them on the prepared baking sheets. Brush the slices with the egg wash and sprinkle with the Parmesan mixture. Bake the crackers for about 17 minutes, or until golden brown. Let cool on the baking sheets. Transfer the crackers to a large plate and serve.
Cut the butter into 4 pieces before adding it to the food processor. The flour and butter reach the desired consistency faster.
You can substitute other salted nuts, such as pecans or walnuts for the macadamias if you like.