Combine 4 ounces chopped white chocolate and 2 tablespoons shortening in top of a double broiler; bring water to a boil. Reduce heat to low; cook until mixture is melted and smooth. Remove from heat. Drizzle melted white white chocolate mixture ocer cooled cake. Melt remaining half cup mini-morsels and 2 teaspoons shortening in a small saucepan over low heat, and let cool; drizzle over white chocolate. If desired, garnish with chocolate and white chocolate leaves.