Carrot Cake with Ginger Mascarpone Frosting

• 2 cups sugar
• 1 1/3 cups vegetable oil
• 3 extra-large eggs, at room temperature
• 1 teaspoon pure vanilla extract
• 2 cups plus 1 tablespoon all-purpose flour
• 2 teaspoons ground cinnamon
• 2 teaspoons baking soda
• 1 1/2 teaspoons kosher salt
• 1 pound carrots, grated (see Cook's Note)
• 1 cup raisins
• 1 cup chopped walnuts
• Ginger Mascarpone Frosting, recipe follows
• Crystallized ginger (not in syrup), chopped, for garnish

Ginger Mascarpone Frosting:

• 12 ounces Italian mascarpone cheese, at room temperature
• 4 ounces cream cheese, at room temperature
• 2 cups sifted confectioners' sugar
• 2 tablespoons heavy cream
• 1/2 teaspoon pure vanilla extract
• 1/3 cup minced crystallized ginger (not in syrup)
• 1/4 teaspoon kosher salt