Green Velvet Cupcakes

Ingredients

• 1 cup cake flour (not self-rising)
• 2 tablespoons unsweetened cocoa powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 3/4 cup sugar
• 1/2 cup milk
• 1/2 cup vegetable oil
• 1 large egg
• 1 tablespoon distilled white vinegar
• 1 teaspoon pure vanilla extract
• 1/2 teaspoon green gel food coloring
• 2 ounces white chocolate (, chopped)
• 3 large egg whites (, at room temperature)
• Pinch Pinch of cream of tartar
• 2 sticks unsalted butter (, cut into pieces, at room temperature)
• Assorted green sprinkles (, for decorating)