Makes about 36 biscotti (3/4-inch-wide cookies)
3 cups unsalted whole almonds
1 cup granulated sugar
1 cup light brown sugar
1/2 teaspoon ground cinnamon
2 teaspoons baking powder
2 1/2 cups all-purpose flour
3 jumbo eggs (or 4 large eggs), plus 1 egg, lightly beaten, for brushing tops of loaves
1 teaspoon pure vanilla extract
Zest of 1 large orange (1 to 2 teaspoons)
Position racks in the upper and lower thirds of the oven and preheat to 350 degrees. Line 2 large baking sheets with parchment paper.
Place almonds in a single layer on a baking sheet and toast in the 350-degree oven for 10 minutes. Remove and set aside.
In a large bowl, hand mix toasted almonds, sugars, cinnamon, baking powder and flour.
In a small bowl, whisk eggs. Add the vanilla and orange zest and whisk until well blended. Add to the flour mixture. Stir a few times. Work the batter together with lightly floured hands. The mixture will be sticky, but persevere. Keep squeezing the batter with your hands until a dough starts to form. Once the dough is firm, form a ball. Divide the ball into 4 equal pieces.
On a lightly floured surface, place 1 piece of dough, and using your hands, roll into a log shape that is approximately 8 inches long, 2 inches wide and 3/4 of an inch high. If it's sticky, simply dust your palms with more flour. Repeat with remaining 3 pieces of dough. Place 2 logs per baking sheet. Brush loaves all over with lightly beaten egg.
Bake for 40 minutes, rotating pans halfway through, or until the tops of the loaves are shiny and deep golden. Cool on a rack for about 20 minutes before slicing.
Place a loaf on a cutting board. Using a large serrated knife, cut 3/4-inch-thick slices, either straight or on the diagonal. Use a sawing motion to prevent crumbling. Each loaf should yield 9 to 11 cookies. If the cookie is crumbling, then let it cool a few more minutes. Don't let it rest too long, however, or it could become too hard to slice.
Place slices on their sides back on the baking sheets. Place in the still warm oven with the temperature off and the door closed for 30 to 60 minutes. The longer they stay in the oven, the harder they will become. Remove from oven and cool completely before storing in an airtight container, preferably a tin, which helps keep them crisp. Stored properly, biscotti will last up to a month.