For the biscotti:
Whole unblanched almonds — 3/4 cup (4 ounces; 100 grams)
Whole pistachios — 1/3 cup (1.6 ounces; 50 grams)
Cold unsalted butter, cubed — 7 tablespoons (3.5 ounces; 100 grams)
Granulated sugar — 3/4 cup (5.25 ounces; 150 grams)
All-purpose flour — 2 cups (8.8 ounces; 250 grams)
Anise seeds — 1 tablespoon (0.3 ounces; 8 grams)
Baking powder — 1 teaspoon (0.2 ounces; 6 grams)
Grated zest of 1 lemon
Pinch of salt
2 large eggs
For the egg wash:
1 large egg white, beaten

Prepare the biscotti. Preheat the oven to 300°F (150°C). Spread the almonds and pistachios evenly on a baking sheet and place in the oven. Toast for about 30 minutes, until they are golden brown. You will be able to smell the nuts when they are ready. A good test is to break a nut in half and check to see if it is light brown on the inside. Toasting the nuts brings out their natural flavor. Remove them from the oven and allow to cool completely on the baking sheet on a wire rack.

Place the remaining ingredients in a large mixing bowl and beat with an electric mixer on medium speed until well combined, about 5 minutes; the mixture will hold together in a soft dough. Add the cooled toasted nuts and mix until they are evenly incorporated, about 1 minute. If you are using a hand-held mixer, you may want to knead in the nuts by hand to avoid burning out the motor of the mixer.

Remove the dough from the mixing bowl and place on a very lightly floured work surface. If the dough is sticky and hard to work with, it is too soft. To fix this, flatten it into a disk, cover with plastic wrap, and place it in the refrigerator for a minimum of 1 hour. (When the butter in the dough gets cold, the dough will stiffen.) Remove from the refrigerator and proceed.)

Preheat the oven to 350°F (175°C). Divide the dough into three equal pieces. Use the palms of your hands to roll each piece on the lightly floured work surface into a rope 1 to 1 1/2 inches in diameter. Each rope should be even and fit on your baking sheet lengthwise. If the dough sticks to your hands or to the work surface as you are rolling it, dust it lightly with flour. Roll firmly to remove any trapped air bubbles. (At this stage, you can wrap the dough well in plastic wrap and freeze for up to two weeks. Bring it back to room temperature before baking.)

Place two of the biscotti ropes on a parchment paper-covered baking sheet. You will only have room for two because they spread as they bake. With a pastry brush, lightly brush each rope with the egg white; this will add shine to the baked biscotti. Bake until golden brown, about 30 minues. Remove from the oven and let cool slightly on the baking sheet.

Use a serrated knife to slice the biscotti on a diagonal into 1/2-inch thick cookies. If you do this while the biscotti are still warm, they will not crumble. The biscotti will harden as they cool. If they are still soft when you slice them, place the slices on a baking sheet and bake at 300°F (150°C) for another 10 to 15 minutes. Repeat the baking and cooling procedure with the remaining biscotti rope.