Valentine's Day Shortbread Cookies

Ingredients

• 8 ounces unsalted butter, very soft
• 1/2 cup powdered sugar
• 1 tsp vanilla extract
• 1 & 3/4 cups all-purpose flour
• 1/4 cup cornstarch
• 1 cup unsalted butter, room temperature
• 3 & 1/2 cups powdered sugar, sifted
• 2 tsp vanilla extract
• 2 tbsp whole milk or heavy whipping cream, room temperature
• 1/4 tsp salt, or to taste
• red, pink, purple gel food coloring