Good-Cooking - Spiced Sweet Potato Cake with Brown Sugar Icing

Ingredients

• 4 (8 ounce) red skinned sweet potatoes (yams)
• Nonstick vegetable oil spray
• 2 3/4 cups all-purpose flour
• 2 teaspoons ground cinnamon
• 1 1/4 teaspoons ground ginger
• 1 teaspoon baking powder
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 2 cups granulated sugar
• 1 cup vegetable oil
• 4 large eggs
• 1 teaspoon vanilla extract
• 1 cup powdered sugar
• 3/4 cup (packed) dark brown sugar
• 1/2 cup whipping cream
• 1/4 cup (1/2 stick) unsalted butter
• 1/4 teaspoon vanilla extract