All American Vanilla Buttercream Cupcakes

Ingredients

• 1-1/2 cup all purpose flour
• 2 Tbsp cornstarch
• 1 cup granulated sugar
• 1 tsp baking powder
• 1/2 tsp baking soda
• 1/4 tsp sea salt
• 6 Tbsp salted butter, at room temperature
• 3 Tbsp vegetable oil (or any neutral cooking oil)
• 1/4 cup water, at room temperature
• 1/2 cup full fat sour cream, at room temperature
• 1 tsp white vinegar
• 2 Large Rosemary Farm Eggs + 1 Egg Yolk, at room temperature
• 1 Tbsp pure vanilla extract
• 1-1/2 cup butter, at room temperature
• 3 tsp pure vanilla extract
• 5-1/2 cup powdered sugar
• 2-4 Tbsp heavy cream