Best Confetti Cake Recipe - Homemade Funfetti Birthday Cake

Ingredients

• 1 1/2 c. (3 sticks) butter, softened
• 2 1/4 c. granulated sugar
• 4 large eggs
• 1 tbsp. pure vanilla extract
• 3 c. all-purpose flour
• 1/4 c. cornstarch
• 2 tsp. baking powder
• 1 tsp. kosher salt
• 1 1/4 c. milk
• 1/2 c. sprinkles, plus more for garnish, if desired
• 1 1/2 c. softened butter
• 6 c. powdered sugar
• 1/4 c. sour cream
• 1 tsp. pure vanilla extract
• 1/4 c. heavy cream
• Pinch of kosher salt