Best Napoleon Cake Recipe - How to Make Napoleon Cake

Ingredients

• 8 large egg yolks (112 g.) 
• 1/2 c. (56 g.) cornstarch
• 1/2 tsp. kosher salt 
• 1 c. (200 g.) granulated sugar, divided
• 4 c. (946 mL) whole milk
• 4 tbsp. (1/2 stick; 57 g.) butter, room temperature
• 4 tsp. vanilla extract
• 2 c. (473 mL) heavy cream
• 2 (1-lb.) boxes puff pastry, thawed
• All-purpose flour, for rolling
• Mixed fresh berries, for serving