In a medium saucepan, combine the water and butter over medium heat. Bring to a boil, stirring until the butter has melted.

Remove from heat and add in the flour and salt all at once. Stir vigorously until it forms a ball.

Return to low heat for 1-2 minutes to dry it slightly, stirring continuously.

Transfer the mixture to a bowl and let it cool for a few minutes. Then, add the eggs one at a time, mixing until fully incorporated before adding the next one. You are looking for a smooth and glossy batter.

Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

Use a piping bag to pipe the dough into long strips on the prepared baking sheet.

Bake for about 25-30 minutes, or until they’re golden and puffy. Keep the oven door slightly ajar during the last 5 minutes to let steam escape.

In a large bowl, whip together the heavy cream, mascarpone cheese, powdered sugar, dissolved coffee, and vanilla extract until stiff peaks form.

Once the eclairs have cooled completely, cut them in half and fill them with the tiramisu cream using a piping bag.

Dust with cocoa powder and drizzle with dark chocolate before serving.