In a large bowl, cream together butter, sugar, orange or lemon zest and vanilla. Mix until light and fluffy. Mix in eggs and egg white one at a time, beating well after each addition. Sift together the flour, baking powder, and salt, gradually blend into the creamed mixture using a wooden spoon. Stir in the white chocolate, candied angelica and pistachios. Cover and chill for 30 minutes or until dough is no longer sticky.
Preheat oven to 325º. Line a baking sheet with parchment paper. Turn cough out on a lightly floured surface, and divide into halves. Form each half into a flattish log about 12 inches by 3 inches wide. Arrange logs at least 3 inches apart on the baking sheet.
Bake for 30 minutes in a preheated oven or until pale gold. Allow logs to cool on the baking sheet until cool enough to handle. On a cutting board, cut logs crosswise on a diagonal into 1 inch thick slices. Arrange on the baking sheet. Bake for an additional 15 minutes or until golden. Transfer biscotti to wire racks and cool completely. Store in an airtight container at room temperature.
Cut angelica stalks in their second year. Unlike many other plants, the big stalks are better as long as they are still green (not purple or white). *April seems to be the month that is most favored for gathering angelica stalks. Recipes for Candied Angelica date back to 1700 and most likely even prior to that time, angelica has been used medicinally and in culinary use as a sweet treat and replacement for dried fruits and berries.
Remove leaves and leaf stalks and cut into pieces of about 3 to 8 inches in length. Soak in cold water for about 8 hours.
Bring the sugar and water to a boil, stirring and then remove from the heat.
Bring a large pan of water to boil and add the angelica stems. Boil until the stems begin to soften, about 4 to 6 minutes. Add about 1/2 teaspoon of baking soda per pint of water to keep the vivid green color which is associated with ‘real’ candied angelica often found in France. It also helps soften the stalks. They will have a sharp, bitter aroma.
Cool under running water, drain and then peel removing the long stringy parts on the outside of the stalks. A vegetable peeler may help, but most of the skin should rub off with your fingers.
Put them into a bowl and pour the hot syrup over them. Weight them with a plate and soak for 24 hours.
Drain off the syrup into a pan. Boil it until it thickens (225º) and pour it over the angelica. Let it cool and keep soaking. Repeat once a day for 3 days, by which time the angelica should be translucent without losing shape.
Remove the angelica stalks from the pan and let them drain on a covered rack or screen until dry and glossy. You might like to roll the stalks in sugar before drying them on the rack.
Store in an airtight tin or jar in a cool dark place. They will last up to 2 years in the right storage conditions.
Cut the stalks into the lengths needed and use to decorate cakes, trifles, desserts or ice cream. Use in recipes in place of dried fruits.