Place the 2/3 cup cashews in a food processor. Cover and process for 2 to 3 minutes or until a smooth butter forms, scraping down sides of bowl occasionally. Transfer cashew butter to a large mixing bowl. Add the 1/3 cup shortening and the butter. Beat with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, brown sugar, baking powder, and baking soda. Beat until combined, scraping sides of bowl occasionally. Beat in eggs and vanilla until combined. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour. Divide dough in half. Cover and chill dough for about 3 hours or until easy to handle.

Preheat oven to 375 degrees F. On a lightly floured surface, roll half of the dough 1/4 inch thick. Using a 2-1/2-inch leaf-shape cutter, cut out dough. Place cutouts 2 inches apart on an ungreased cookie sheet. Repeat with remaining dough.

Bake in preheated oven for 6 to 8 minutes or until edges are firm and bottoms are light brown. Transfer to a wire rack and let cool.

In a small heavy saucepan, melt white chocolate and the 4 teaspoons shortening over low heat, stirring frequently. Spread a thin layer of the white chocolate mixture over the bottom of each cookie. Place cookies, white chocolate side up, on a wire rack placed over waxed paper. Immediately sprinkle the very finely chopped cashews on cookies. Let stand until set. Makes 60.

Place cookies in layers separated by waxed paper in an airtight container; cover. Store at room temperature for up to 3 days. Or freeze unfrosted cookies for up to 3 months; thaw and decorate.