1. Preheat oven to 350 degrees F. Using two muffin tins, line 15 muffin cups with paper liners and spray liners with nonstick vegetable oil spray.
2. Make cupcakes. Into a large bowl, sift flour, baking soda, salt, and cinnamon. Add sugar and use an electric mixer on low speed to mix, just to combine ingredients. Mix in oil. The mixture will look crumbly. Mix in eggs until smoothly blended, about 30 seconds. Stir in carrots and chopped walnuts.
3. Using a 1/4-cup measuring cup, divide batter evenly among 15 lined muffin cups; do not overfill. Bake just until a toothpick inserted in center of cupcake comes out clean and top is golden, about 20 to 25 minutes. Cool cupcakes for 10 minutes in pan on a wire rack. Transfer cupcakes in their paper liners to wire rack to cool completely, about 30 minutes.
4. Make frosting. Stir white chocolate in top of double boiler over simmering water until melted and smooth. Alternatively, melt in microwave for 1 minute, then stir. Heat for an additional 30 seconds until chocolate is melted and smooth.
5. In a large bowl, use an electric mixer on medium speed to beat melted white chocolate, butter, cream cheese, and vanilla together until blended. Add confectioners' sugar; beat on low speed until frosting is smooth.
6. Use a small metal spatula to spread frosting over top of each cupcake. Press a walnut half into top of each. Cupcakes can be covered and refrigerated for up to two days.
Source: Hannaford fresh Magazine, March - April 2007