Preheat oven to 350 degrees.
Prepare Holiday Tree Pan. Use pastry brush to thoroughly coat all parts of pan with shortening. Sprinkle flour evenly over top of shortening; invert pan and shake out excess.
Cream shortening and sugar in large mixing bowl until thoroughly blended. Separate eggs and reserve yolks. Add whites to shortening mixture and beat an additional two minutes or until light and fluffy. Beat in white chocolate instant pudding mix, peppermint extract, yogurt OR sour cream (mixture may look curdled).
Sift flour, salt and baking powder together. Slowly beat in about half of flour mixture, then ¾ cup milk, then last of flour mixture, scraping bowl after each addition. Increase speed and beat until thoroughly combined, 2-3 minutes.
Remove two cups of batter, stir in white chocolate chips or chunks.
Dollop white chocolate batter into pan. Do not try to make it smooth and even. Keep it unevenly distributed in peaks and on sides. Push gently up against sides. Add reserved yolks, cocoa; fudge pudding mix and additional ¼ cup milk to rest of batter in bowl. Beat until completely combined. Stir in chocolate chips.
Layer chocolate batter over top of white batter; push gently up against sides. Gently tap the filled pan on the counter a few times to remove air bubbles and pockets.
Place pan on cookie sheet. Bake in preheated 350-degree oven for 50-60 minutes or until wooden skewer inserted in center of cake comes out clean (do not use a metal skewer). Cool in pan ten minutes, shake pan from side to side to check for thumping or loosening from sides of pan. If needed, use a plastic knife to carefully loosen the cake from center and sides, if stuck. Invert onto cooling rack.
When completely cooled, dust tops with confectioner’s sugar. Place on platter and arrange sprigs and crushed candies around edge of platter at bottom of cake.