1 cup vegetable oil 2 cups granulated sugar 3 large eggs 2 teaspoons vanilla 3 cups flour 2 teaspoons ground cinnamon 1 teaspoon baking powder 1 1/2 teaspoon baking soda 1 teaspoon salt 2 cups grated carrots 1 1/2 cup fresh or frozen blueberries, not thawed ***WHITE CHOCOLATE FROSTING (OPTIONAL)*** 3 ounces good quality white chocolate, chopped 4 ounces regular or light cream cheese, at room temperature 2 cups powdered sugar, sifted if lumpy 3 tablespoons regular or low-fat sour cream
Preheat oven to 350 degrees F. Spray a 9- by 13-inch baking pan with cooking oil spray. Line bottom of pan with parchment or wax paper and spray the paper.
In a mixing bowl with electric mixer, beat oil and sugar on medium speed until light and fluffy, about 2 minutes. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla.
Add flour, cinnamon, baking powder, baking soda and salt. Mix on low speed until combined. Mix at medium speed 2 minutes. Add carrots and mix on low to blend. Fold in blueberries. Batter will be stiff. Pour into prepared pan, smoothing the top.
Bake for 60 to 70 minutes or until top is golden and toothpick inserted in center comes out clean. Cool 10 minutes and invert onto rack. Pull off paper and cool.
For Frosting: Melt chocolate in a small microwave-safe bowl at 50% power for 60 to 90 seconds or until smooth, stirring once. Or melt on stove in double boiler. Cool slightly.
In a mixing bowl, beat cream cheese and powdered sugar until very smooth, about 2 minutes. Mix in chocolate; it will look grainy. Add sour cream and mix until smooth, about 1 minute.
Spread a thin layer of frosting over the top and sides of cake. Spread remainder to cover as smoothly as possible. Refrigerate until set. Serve cake chilled or at room temperature.