Preheat the oven to 350 degrees F.

Line a baking sheet with parchment paper. Sift together flour and baking powder and set aside. In a mixer, beat the sugar, butter, lemon zest and salt. Beat in the eggs, 1 at a time. Add the flour mixture and beat just until blended. Stir in the cranberries and half of the mini chocolate chips.

Form the dough into a 12-inch long, 3-inch wide log on the parchment lined baking sheet. Bake for 40 minutes. Remove and let cool completely.

Place the log on the cutting board. Using a sharp serrated knife, cut the log on a diagonal into 3/4-inch-thick slices. Arrange the biscotti on the baking sheet. Bake the biscotti again, for 15 minutes, until they are golden brown. Transfer the biscotti to a rack and cool completely.

Melt the white chocolate chips in a double boiler. Dip the bottom of the biscotti in the white chocolate and let chocolate cool and set.

Melt the remaining chocolate chips and drizzle over the white chocolate to decorate.