Preheat the oven to 350°F.

1. For the pastry, mix the butter and icing sugar together in a robot, then add the egg and flour and instant espresso little by little to obtain a smooth pastry.

2. Shape the pastry into a ball and wrap it in plastic wrap. Refrigerate for 40 minutes.

3. Meanwhile, prepare the coffee filling by mixing the eggs with the cream in a clean robot.

4. Add the brown sugar, instant coffee, and chestnuts. You will then have a smooth filling. Set aside.

5. Roll out the coffee tart pastry and line your tart mold, then fill the tart with the coffee filling to the top.

6. Bake for 30 to 45 minutes. Hot or cold, this tart is a real delight!