Heat oven to 325°F. Line a large baking sheet with parchment.
Cream butter and sugar until light and fluffy.
Beat in eggs one at a time. Mix in vanilla, almond extract, and orange zest.
Whisk flour, baking powder, and salt. Add to bowl and mix until a soft dough forms.
Fold in pistachios and cranberries until evenly distributed.
Shape dough into a 12x3-inch log on the sheet. Smooth with damp hands.
Bake 25–28 minutes, until set and lightly golden. Cool 10 minutes.
Reduce oven to 300°F. Transfer log to a board.
Slice into 1/2-inch pieces with a serrated knife. Lay slices cut side down.
Bake 10 minutes. Flip and bake 8–12 minutes more, until dry and crisp. Cool completely.
Melt white chocolate and drizzle over cooled biscotti. Let set before serving.