Preheat oven to 350 degree F. Line cookie sheet with parchment paper. Beat butter with mixer on medium to high speed 30 seconds. Add sugar, soda, baking powder, and salt; beat until combined. Add eggs, lemon peel and juice, and extract. Beat until combined. Add flour; beat until combined. Stir in nuts. Divide dough in half. Shape each into a 12-inch roll. Place at least 3 inches apart on baking sheet. Bake 35 to 40 minutes or until beginning to brown (logs will spread). Cool completely on a rack. Use a serrated knife to cut each roll into 3/4-inch slices. Place, cut sides down, on ungreased cookie sheet. Bake in 350 degree F oven for 5 minutes. Turn slices over; bake 5 minutes more or until dry and crisp. Cool on rack.

Combine 1/4 cup finely chopped pistachio nuts and 1/4 cup finely chopped macadamia nuts. In small saucepan melt 8 to 10 ounces white chocolate baking squares over low heat. Stir in 1 teaspoon finely shredded lemon peel and 1 tablespoon shortening. Add additional shortening, 1 teaspoon at a time, until of dipping consistency. Dip 1 end of biscotti into white chocolate; sprinkle with nuts. Dry completely. Makes 36 biscotti.