Beat butter at medium speed of an electric mixer 2 minutes or until creamy. Gradually add sugar, beating at medium speed 5 to 7 minutes. Add eggs, one at a time, beating just until yellow disappears.
Combine sour cream and soda. Add flour to butter mixture alternately with sour cream mixture, beginning and ending with flour. Beat at low speed just until blended after each addition. Stir in white chocolate and next 3 ingredients. Pour batter into a greased and floured 10" tube pan.
Bake at 325° for 1 hour and 15 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan on a wire rack 10 to 15 minutes; remove from pan. Let cool completely on wire rack.
Line a jellyroll pan with wax paper; place under wire rack (to catch excess glaze). Working quickly, pour White Glaze over top of cake, pushing glaze down sides of cake with a spatula to cover cake completely. Let stand at least 1 hour. Transfer cake to a pedestal or other serving piece.
Using green gel, outline (freehand) leaves on top and sides of frosted cake. Add an additional small amount of green gel to center of each leaf; spread with wooden picks, filling in leaves completely.
Dot 1 end of each holly leaf with a small amount of black gel. Beginning at black dot at the base of each leaf, drag wooden pick down center; then drag wooden pick from center black line to tips of each leaf, creating veins. Using red gel, add 1 to 3 dots around base of each leaf to form holly berries.
Note: For white chocolate, we used Baker's.
Note: Find little tubes of decorating gel at the grocery store near the baking section. You'll be surprised how easy it is to draw these holly leaves.