Preheat oven to 180 degrees C and place rack in center of oven. Line a baking pan with parchment paper.

In the bowl with a hand mixer, beat the butter and sugar until light and fluffy (2-3 minutes). Add the eggs and egg yolk, one at a time, mixing well after each addition. Beat in the vanilla extract. Scrape down the sides of the bowl as needed.

In a separate bowl, whisk together the flour, baking powder, salt, and cocoa powder. Add to the butter mixture and beat until incorporated. Stir in the dried cranberries and white chocolate chips.

Transfer the dough to a floured surface and divide it in half. Form each half into a log 10 inches (25 cm) long. Do this by rolling the dough back and forth into a cylinder shape with floured hands.

Transfer the logs to the baking sheet, spacing them well apart (width-wise on the pan), and pat to even the shapes.

Bake until firm to the touch, about 25 - 30 minutes (logs will spread during baking). Remove from the oven, place on a wire rack, and let cool for about 10 minutes.

Using a long spatula transfer the logs to a cutting board. Using a serrated knife, cut the logs into slices about 3/4 inch (2 cm) thick on the diagonal.

Arrange the slices on the baking sheet and bake on about 8 - 10 minutes. Turn the slices over and bake until crisp and dry, about 8 - 10 minutes longer. Remove from oven and let cool on wire rack.

Makes about 24 - 30 biscotti

Optional-Melt 3 90 grams of chopped white chocolate and 1 teaspoon of vegetable shortening in a small metal bowl placed over a saucepan of simmering water. Watch carefully as white chocolate can burn easily. Stir to melt. Remove from heat and with an offset spatula spread a layer of white chocolate on one side of the biscotti (or dip one end into the melted chocolate). Let the chocolate dry on a parchment-lined baking sheet.