PART 1 OF DIPLOMAT CREAM

1. Mix the yolks, sugar, salt and cornstarch - In a heat-proof bowl, mix the yolks, the last half of the granulated sugar, salt and cornstarch. Whisk until smooth and pale, about 2 minutes.
2. Warm the milk, vanilla bean, and sugar - Cut the vanilla bean in half and scrape the insides with a knife to release the seeds. Add both the pod and the seeds to a small pot with milk and half of the granulated sugar, and cook over a medium low heat, stirring occasionally. As soon as it reaches a boil, immediately remove the pan from the heat.
3. Temper the eggs - Slowly add half of the warmed milk to the egg mixture and mix evenly. Make sure you are whisking constantly! Then add the egg mixture back into the hot milk in the pot.
4. Cook the cream - For 1-2 minutes, heat the custard over medium heat while stirring constantly until the batter becomes thick and comes to a boil. When large bubbles begin to break the surface of the custard, lower the heat and let it continue to cook for another minute, whisking constantly.
5. Strain - Remove from the heat and run the pastry cream through a fine mesh sieve to remove lumps and any burnt bits from the pot.
6. Add the butter - Stir in the butter until melted.
7. Chill - Pour the finished pastry cream into a shallow bowl and cover the entire surface with plastic wrap to prevent a skin from forming. Once the pasty cream is at room temperature, refrigerate at least 2 hours before using.

CRAQUELIN

1. Combine all ingredients - With a stand mixer fitted with a paddle attachment, cream the butter and brown sugar together until smooth. Add in the flour just until a dough forms.
2. Roll - Place the dough on a piece of parchment paper with a second piece on top. Roll it out to a thickness of 2-3 mm.
3. Chill - Chill for about 1 hour in the fridge (or 20 minutes in the freezer) until firm.

CHOUX PASTRY

1. Preheat - Preheat oven to 400°F (204°C). Line a baking sheet with non-stick baking mat or parchment paper. Using a 2 inch cookie cutter covered in flour, stamp circles leaving 2 inches in between each. 
2. Cook water, milk, sugar, salt, and butter - Add water, milk, sugar, salt and unsalted butter in a pot and cook over medium heat until it comes to a boil.
3. Add flour - Remove the pot from the heat and add in the sifted flour all at once. Mix until you see no lumps. This is called the panade.
4. Cook the panade - Return to the heat and cook over medium heat for 1-2 minutes. You should see a thin layer of film stick to the bottom and sides of the pot.
5. Cool - Transfer the dough to a bowl of a stand mixer fitted with a paddle attachment and beat at medium speed for about 1-2 minutes to cool the dough faster. But if you don’t have a stand mixer, you can let it stand at room temperature for 5 minutes.
6. Slowly add the eggs - In a small measuring cup, slightly beat all the eggs. Add the egg mixture into the dough in three additions. Make sure to stir well between additions until the egg is fully incorporated. The batter might look like it’s curdled, but that is normal. Just continue to keep beating. You will know when the batter is ready when you lift the dough with a spatula and it hangs in a smooth inverted triangle shape.
7. Pipe mounds - Transfer the batter to a prepared pastry bag fitted with a round piping tip. Hold the piping bag at a 90° angle and pipe 2 inch mounds onto the baking sheet (using the traced circles as a guide). If you have leftover batter, wait until this batch is done baking to pipe more choux mounds on your second baking sheet.
8. Cut out discs - Take out the chilled craquelin dough and cut out discs using the same 2 inch round cookie cutter. carefully place one on top of each piped choux mound. Keep leftover discs in the freezer until you need them.
9. Bake - Bake the choux at 400°F (204°C) for the first 10 minutes, then decrease the temperature to 375°F (190°C) for the last 20-25 minutes, until the choux are puffed and deeply golden brown. Do not open the oven door at this time! Remove from oven when done and poke a hole on the side of each puff to release any extra steam.
10. Cool - Once done, let the choux cool on top of the stove while still on the baking sheet. Once cooled for about 10 minutes, transfer them to a wire rack to cool completely.

PART 2 OF DIPLOMAT CREAM

1. Make the whipped cream - In a mixing bowl, whip the cold heavy whipping cream and sugar in a chilled metal bowl until you see medium peaks.
2. Combine the pastry cream and whipped cream together - Whip the cold pastry cream with a whisk to make it soft. Fold in only 1/3 of the whipped cream to the pastry cream in two additions, and mix evenly. Save the other 2/3 of the whipping cream for assembly.
3. Assemble - Using a serrated knife, slice just the tops of each choux. Using a wider end of a round piping tip, stamp the choux tops to cut out perfect circles. Fill each choux first with the diplomat cream, then layer with strawberries and blueberries, and finally pipe on the whipped cream. Place the choux tops and top with powdered sugar.