Preheat oven to 300 degrees. Line twp baking sheets with parchment paper and set aside. Put the sugar and orange zest in large bowl (or stand mixer) and use your fingers to rub the zest into the sugar. This infuses the sugar with orange and gives the biscotti a lovely zesty flavor.
Add the oil and mix with the orange-infused sugar. Add vanilla and eggs and mix completely. Add the flour, salt, and baking powder and stir with a wooden spoon to combine (or mix in the stand mixer). Fold in chopped cranberries and pistachios (and chocolate chips if you are making the Double Chocolate version).
Divide dough in half and place one half on each baking sheet. Form two logs about 12 x 2 inches long. Bake for 35 minutes, until logs are light brown. Remove from the oven and cool for 5-10 minutes. Reduce oven to 275 degrees.
Use a very sharp knife (I use a straight chef's knife instead of serrated to get very clean lines) and cut logs on the diagonal into 3/4-inch slices. Aim to get 12 slices out of each log, for a total of 24 pieces.
Turn sliced biscotti cut-side down on the baking sheets and bake for another 8-10 minutes. Set on a wire rack to cool (they will crisp up as they cool). After the biscotti have cooled, drizzle with melted almond bark or white chocolate and devour!