Mini Tiramisu Éclairs
- For the pastry puffs:
- 6 tablespoons unsalted butter (3/4 stick), cut into 6 pieces
- 1/4 cup plus 2 tablespoons whole milk
- 1/4 cup plus 2 tablespoons water, plus more as needed
- 1 tablespoon granulated sugar
- 1/4 teaspoon fine salt
- 3/4 cup all-purpose flour
- 3 large eggs, at room temperature
- For the filling:
- 1/2 cup cold heavy cream
- 1/2 cup cold mascarpone cheese (about 4 ounces)
- 2 tablespoons sweet Marsala wine
- 2 tablespoons powdered sugar
- 1/2 teaspoon vanilla extract
- For the glaze:
- 2 tablespoons heavy cream, plus more as needed
- 2 tablespoons sweet Marsala wine
- 1 teaspoon instant espresso powder
- 1 cup powdered sugar, sifted
- To assemble:
- 1 tablespoon Dutch-process or unsweetened natural cocoa powder
For the pastry puffs:
Heat the oven to 425°F and arrange a rack in the middle. Line a baking sheet with parchment paper; set aside.
Heat the butter, milk, measured water, sugar, and salt in a medium heavy-bottomed saucepan over medium-high heat until the butter has melted and the liquid has come to a boil. Reduce the heat to low, add the flour all at once, and stir vigorously with a wooden spoon until well incorporated. Cook, stirring constantly, until the dough looks shiny and feels smooth to the touch, and a thin film has formed on the bottom of the pan, about 5 minutes. (The dough will easily form 1 large ball.)
Transfer the dough to the bowl of a stand mixer fitted with a paddle attachment and let it cool for 5 minutes. Meanwhile, fill a small bowl with water and set it aside.
With the mixer on medium-low speed, add 1 of the eggs and beat until completely incorporated, at least 1 minute. Add the second egg and beat until completely incorporated, at least 1 minute. Stop the mixer and scrape down the beater and the sides of the bowl with a rubber spatula. Return the mixer to medium-low speed, add the remaining egg, and beat until the mixture is smooth, sticky, and glossy, at least 1 minute more.
Transfer the dough to a large piping bag fitted with a 1/2-inch round tip. (Alternatively, place the dough in a large resealable plastic bag and cut off about 1/2 inch from one bottom corner.) Pipe 20 (2-1/2-by-1-inch) fingers onto the prepared baking sheet, making sure they’re about 1 inch apart. Gently pat down any wispy tips with a finger dipped in the reserved bowl of water.
Place the baking sheet in the oven, reduce the temperature to 350°F, and bake until the puffs are golden brown, airy, and completely dry inside, about 30 to 35 minutes (do not open the oven door until at least 30 minutes has passed). Transfer the baking sheet to a wire rack and let the puffs cool completely, at least 20 minutes.
For the filling:
When ready to serve, place all of the filling ingredients in the bowl of a stand mixer fitted with a whisk attachment. Whisk on low speed until the powdered sugar is just incorporated. Increase the speed to high and whisk until medium peaks form, about 30 seconds more.
Transfer the mixture to a large piping bag fitted with a 1/2-inch round tip. (Alternatively, place the filling in a large resealable plastic bag and cut off about 1/2 inch from one bottom corner.) Place in the refrigerator while you make the glaze.
For the glaze:
Whisk the cream, Marsala, and espresso powder together in a medium bowl until smooth. Add the powdered sugar and whisk until smooth; set aside. (If the mixture is too thick to easily run off a spoon, whisk in more cream 1/2 teaspoon at a time.)
Using a paring knife, cut a slit in the long side of each éclair, being careful not to cut all the way through the pastry. Gently open up the éclairs. Remove the filling from the refrigerator and pipe it into the bottom half of each éclair. Close the éclairs. Carefully pick them up with your fingers, dip the tops in the glaze, then return them to the baking sheet glaze-side up.
Place the cocoa powder in a fine-mesh strainer and sift it generously over the tops of the éclairs. Let sit until the glaze sets, about 30 minutes.