Gather all your ingredients to ensure you have everything on hand.

Heat the milk in a saucepan, adding the instant coffee until it’s hot but not boiling.

In a separate bowl, whisk together the egg yolks, sugar, and cornstarch until you get a light, pale mixture.

Slowly pour the hot coffee-infused milk into the egg mixture while whisking continuously to prevent curdling.

Return this mixture to the pot and cook over medium heat, stirring constantly until it thickens.

Stir in the butter and vanilla until fully incorporated and chill covered with plastic wrap.

Prepare the optional craquelin topping by mixing butter, brown sugar, and flour until it forms a dough; roll out and freeze.

Preheat your oven to 400°F (200°C).

Combine the butter, water, sugar, and salt in a saucepan and bring to a boil. Add the flour all at once, stirring vigorously.

Remove from heat and let the dough cool for about five minutes.

Add eggs one at a time, mixing until the mixture is smooth and shiny.

Pipe small mounds onto a parchment-lined baking tray. If using, cut and place the frozen craquelin on top.

Bake at 400°F for 10 minutes, reduce temperature to 350°F, and bake for another 15-20 minutes until golden.

Let choux puffs cool completely before filling.

Make a small hole at the bottom of each cooled puff and fill them with the chilled coffee pastry cream using a piping bag.

Serve cold for the best flavor.