Step 1

In a mixing bowl, whisk together eggs, granulated sugar, and cornstarch until combined. Set aside.

Step 2

In a small pot, heat milk on medium heat until it comes to a simmer. Sift in matcha powder and whisk to combine. Slowly pour the hot milk into the egg mixture while whisking vigorously to temper the eggs.

Step 3

Pour the entire mixture back into the pot and return it to medium heat. Keep stirring constantly for about 8-10 minutes until the mixture thickens into a custard-like consistency. If you drag a spatula through the pastry cream, it should part and then come back together after 1-2 seconds.

Step 4

Stir in butter cubes one at a time until all melted and combined. Push the pastry cream through a fine mesh sieve (optional but recommended) into a bowl and press a piece of plastic wrap right onto the surface of the custard to prevent a skin from forming. Let cool completely and store in the fridge for later.

Step 5

In a small bowl, use a silicone spatula to cream together the softened butter and sugar until it becomes a smooth paste. Mix in flour until it becomes a soft dough.

Step 6

Turn the dough out onto a piece of plastic wrap and press together to form a flattened disc.

Step 7

Fold the plastic wrap on top of the dough (to prevent it from sticking to your rolling pin) and use a rolling pin to roll it out to about 1/8" thick. Freeze for at least 1 hour or overnight until it is a solid sheet.

Step 8

Preheat oven to 400°F and line a baking sheet with parchment paper. Set aside.

Step 9

In a small pot, melt together butter, water, and milk on medium heat until it comes to a simmer. Bubbles must be coming to the surface. Add the flour in all at once and quickly stir it together right away until it forms a soft dough.

Step 10

Keep stirring the dough around the pot, flattening it out, and spreading it around for about 4 minutes to dry it out. It should look like dry mashed potatoes. Remove from heat and let cool for 5-10 minutes until barely warm to the touch.

Step 11

Add in the eggs 1/3 at a time, stirring until the dough has absorbed the eggs in between additions. It will look like it's curdled for a bit but just keep stirring until it's smooth and slightly shiny. Your dough is at the right consistency when you scoop it up with a spatula and let it drop back into the pot and it leaves a V-shaped piece of dough on the spatula.

Step 12

Use a 2" cookie/ice cream scooper to scoop the dough out onto your baking sheet, leaving 3" between each choux.

Step 13

Take your frozen craquelin sheet out and use a 2" round cookie cutter to cut out discs. Place the craquelin discs on top of each choux dough mound.

Step 14

Bake at 400°F for 5 minutes. Turn it down to 350°F and bake for another 25-30 minutes until puffs are golden brown. In the last few minutes of baking, use a chopstick to poke a hole into each puff to release any steam inside. Let cool completely before using a serrated knife to cut the tops off (optional).

Step 15

While the choux puffs are cooling, prepare the fillings. In a mixing bowl, use an electric mixer to beat whipping cream until it becomes almost stiff peaks.

Step 16

Add in half of the matcha pastry cream you made earlier and use a silicone spatula to gently fold in an upwards motion to combine without deflating too much air out of the whipped cream.

Step 17

Transfer the diplomat cream and the remaining half of the pastry cream into separate piping bags and snip the tips off the bags.

Step 18

Pipe the diplomat cream into the cooled choux shells until about 4/5 full. Insert the tip of the pastry cream piping bag right into the middle of the diplomat cream and pipe the pastry cream directly into the center of the cream puff until full.

Step 19

Use any remaining diplomat cream to pipe a simple design on top of each cream puff. Serve immediately or within an hour of assembling.