Chocolate St. Honoré Cake

Ingredients

• 2 sheets puff pastry thawed
• 1 cup water
• 1/2 cup unsalted butter
• 1/4 teaspoon salt
• 1 cup all purpose flour
• 4 large eggs
• 2 egg yolks
• 1/2 cup sugar
• 2 tablespoons cornstarch
• 2 tablespoons water
• 1 1/2 cups milk
• 1 tablespoon all purpose flour
• 1/2 cup semi-sweet chocolate chips
• 1/4 cup unsalted butter
• 1 cup chocolate melts, melted
• 8 ounces mascarpone cheese softened
• 2 tablespoons cognac
• 2 cups heavy cream chilled
• 1/2 cup sugar