- Preheat an oven to 350°F. Line three 12-cup muffin tins with decorative cupcake papers.
- To make the cupcakes, in a bowl, sift together the flour, baking soda, baking powder, cinnamon, nutmeg, cloves and salt. Toss the walnuts and raisins with the flour mixture. (This will help prevent them from sinking to the bottom of the muffin tins.)
- In a large bowl, whisk together the pumpkin, granulated sugar, brown sugar and oil. Add the eggs one at a time, whisking after each addition.
- Add the flour mixture in three additions, stirring with a large wooden spoon until just combined.
- Fill the muffin tins about three-fourths full. Bake until the cupcakes are golden and a toothpick inserted into the center comes out clean, 20 to 25 minutes. Transfer the tins to a wire rack and let cool for 10 minutes, then remove the cupcakes from the tins and let cool completely.
- To make the frosting, in a double boiler, melt the white chocolate, stirring constantly, until smooth and creamy, 2 to 3 minutes. Let stand until just warm to the touch. In a large bowl, using an electric mixer, beat the cream cheese and butter on medium-high speed until smooth and blended. Add the melted chocolate and beat again until smooth. Use the frosting immediately, coloring it as desired. Spread 1 to 2 Tbs. frosting over each cupcake and decorate with colored sugars and decorating pens. Makes 36 cupcakes.