Preheat oven to 350° F / 175° C. Line a half-sheet rimmed baking tray with parchment or a silicone baking mat.

In a large bowl, combine all purpose flour, granulated sugar, baking powder, and fine sea salt. Add the cubed butter and use your hands to rub together until the mixture resembles coarse breadcrumbs.

With a bench scraper, work the eggs, almond extract, and orange zest into the dry ingredients until a clumpy dough forms.

With your hands, knead in the dark chocolate, walnuts, and dried cranberries.

On a lightly floured countertop, divide dough into two equal portions, and roll each portion into a log. Each log should measure approximately 8 inches long and about 1 1/2 inches wide.

Arrange logs on prepared tray, allowing plenty of space (at least 4-5 inches) in between.

With a pastry brush, brush the top of each log with beaten egg white.

Sprinkle generously with Demerara sugar.

Bake in preheated oven for 25 minutes, or until tops of logs are dry to the touch. Remove from oven and reduce oven temperature to 325° F / 162° C.

Cool on trays for 10 minutes, then transfer logs to a chopping board. With a serrated knife, slice logs diagonally into 1/2-inch to 3/4-inch slices. Dough may crumble slightly.

Arrange slices upright on prepared tray. Bake for an additional 20-25 minutes, or until dry. (If using two smaller trays, rotate the trays halfway through the bake time.)

Cool completely on a wire rack.

Layer cranberry biscotti in an airtight container between sheets of parchment or wax paper. Store at room temperature for up to 5 days, or freeze for up to 3 months.