Combine cornstarch and ½ cup milk and stir to dissolve. Beat whole eggs and yolks into cornstarch mixture; set aside.
Prepare an ice bath; set aside.
Combine remaining milk with sugar and salt in a saucepan and bring to a boil over medium heat. Remove sauce pan from heat and transfer mixture to a new pan to reduce any residual heat. Set aside and cool milk mixture for 5 minutes.
Slowly add egg mixture into hot milk stirring constantly so the eggs do not curdle. Return mixture to stove top and stir vigorously until mixture comes to a boil. Continue to stir until the whisk leaves a trail in the pastry cream, about 5-7 minutes. Once pastry cream reaches this stage, remove sauce pan from heat and stir in butter and vanilla extract. Transfer the saucepan to the ice bath. Stir occasionally until pastry cream is cool, about 30 minutes.
To make French Toast:
In shallow bowl like a pie pan, whisk together the eggs, half and half, and vanilla bean paste.
Heat a nonstick pan or a griddle. Add butter and let melt. Dip each slice of bread in the egg mixture, making sure that each side is soaked. Let any excess drip back into the bowl.
Place the dipped slice onto the griddle. Repeat with remaining slices. Cook for about 2 to 3 minutes on each side, or until a golden crust forms.
To make Strawberry Coulis:
In a large sauce pan, add fresh strawberries, sugar, and lemon zest and bring to a boil.
Lower heat and cook for 4 to 5 minutes on medium. Transfer mixture to a blender and process until smooth. Store in the refrigerator for up to 2 days.
Place one piece of French Toast down on a plate and layer with pastry cream, fresh sliced strawberries, and strawberry coulis. Repeat once more and top with a third piece of french toast, whipped cream, granola, and additional sliced strawberries, about 2 Tbsp of each.