Chocolate-Mayonnaise Cupcakes With Caramel-Butterscotch Buttercream Frosting

Ingredients

• 2 cups bleached all-purpose flour
• 3/4 cup natural cocoa powder
• 1 teaspoon baking soda
• 1/4 teaspoon salt
• 2 cups sugar
• 2 large eggs
• 1 cup mayonnaise (not low-fat)
• 2 teaspoons pure vanilla extract
• 1 1/3 cups boiling water
• 1 cup granulated sugar
• 3 tablespoons water
• 1 cup heavy cream
• 6 large eggs
• 1 1/2 cups firmly packed dark brown sugar
• 1 teaspoon pure vanilla extract
• 1/4 teaspoon salt
• 1 1/2 pounds cold unsalted butter
• 2 tablespoons bourbon