Chop the white chocolate. Preheat oven to 180C (360F).
In a bowl, sift together flour, green tea and baking powder.
Add sugar and milk and beaten egg, then combine with spatula. (If the dough is too dry, you could add a little milk).
Add mixed nuts using your hands.
Shape into a long roll on a cookie sheet. Flatten to about one inch thickness.
Bake dough in the oven at 360F for 20 minutes. Remove from oven and allow to cool.
Cut into diagonal slices. Place the cut sides down. Bake it in the oven at 320F for about 8 to 10 minutes. Transfer to a rack and cool.
Melt white Chocolate in a double boiler over low heat until melted and smooth. Dip biscotti half-way into the melted chocolate. Place biscotti on a parchment paper. Refrigerate until chocolate is firm.