Make the coconut and lime pastry cream: In a saucepan set over medium heat, combine the milk, coconut cream, and lime zest, and bring it to just a simmer (don’t boil).
Meanwhile, in a large mixing bowl, whisk together the eggs, egg yolk, sugar, and flour. Once the milk mixture is simmering, slowly pour a ladleful into the egg mixture, whisking continuously to gradually heat up the eggs without cooking or curdling them. Continue gradually whisking in the hot milk mixture to the eggs, and when both are fully combined, scrape the mixture back into the saucepan. Cook over medium-low heat, whisking continuously until the mixture has thickened, about 4 minutes. Remove from the heat, whisk for another minute, then add the butter and whisk until fully combined. Strain the custard through a fine-mesh sieve into a clean bowl. Press a piece of plastic wrap directly on the surface of the custard, and let cool to room temperature, then refrigerate until completely cold, at least 2 hours (the custard can be made up to two days in advance).
Make the kiwifruit curd: Place the chopped kiwifruits in a food processor and puree just until smooth. You can also use a stick blender to do this step, but be careful not to over process or blend the fruit so to keep most of the seeds intact. Processing the seeds completely won’t affect the taste or texture, but it will affect the color of the curd, making it duller and grainy-looking. You should get ¾ cup (180 ml) kiwifruit puree. If you are missing some, puree an additional kiwifruit to get the exact quantity.
Transfer the kiwifruit puree to a saucepan, then, off the heat, whisk in the sugar, lime juice, and flour. In a small bowl, beat the eggs and egg yolks together, then add to the kiwifruit puree mixture, whisking to combine. Add the cubed butter, then set the saucepan over medium-low heat. Whisk continuously until the butter melts and the curd thickens, about 10 minutes. Do not boil: the mixture should barely simmer throughout the process. Lower the heat if needed. Remove from the heat, then strain through a fine-mesh sieve into a clean bowl (discard the seeds that don't pass through the sieve). Press a piece of plastic wrap directly on the surface of the custard, and let cool to room temperature, then refrigerate until completely cold, at least 2 hours (the curd can be made up to two days in advance).
Make the choux paste: Position a rack in the lower third of the oven. Preheat the oven to 400°F (200°C).
Measure the flour and set it close to the stovetop.
In a large saucepan, combine the water, milk, butter, and salt. Bring to a boil over medium heat. When the mixture is boiling, add the flour all at once and stir vigorously with a wooden spoon until the mixture pulls away from the sides of the pan. Continue to cook and stir the mixture for about 1 minute to eliminate excess moisture. Transfer to the bowl of an electric mixer and let cool for 5 minutes, stirring occasionally to allow the steam to come out.
Set the mixer to medium speed, and beat the eggs in one at a time, making sure each egg is well incorporated before adding the next. Also scrape the bowl down between each egg addition.
Shape the éclairs: Line a large aluminum baking sheet with parchment paper. If using, slide the éclair templates under the parchment paper for guidance. Use masking or painter’s tape to secure one side of the parchment paper to the baking sheet so it doesn’t move when you pipe the dough.
Hold the bag with the tip at a 45-degree angle. With the tip of the bag touching the sheet, squeeze gently and evenly with one hand, while guiding the tip of the bag with the other. Use gentle pressure to form 1-inch (2.5-cm) wide and 5-inch (12.5 cm) long logs. To stop piping, release pressure from the bag, then push the tip down and quickly jerk it upward to the end the shape without a tail. Pipe all logs, spaced 2-inches apart to allow for expansion.
Remove the masking or painter’s tape, then slide the templates off the baking sheets (if using).
After piping all logs, eliminate tails by dipping a finger in cold water and gently smoothing any peaks sticking out. If desired, take a fork and gently drag it along the length of each éclair to create a signature texture and look. Apply only very gentle pressure: you want to create very light grooves.
Place the baking sheet in the oven, and immediately reduce the oven temperature to 350°F (175°C). Bake for about 40 minutes, or until the éclairs are light brown, rotating the sheet halfway through. Lower the temperature to 300°F (150°C) and bake for an additional 20 minutes, rotating the sheet halfway through. At this point, the éclairs should be golden brown and feel light and hollow. If the éclairs are still light in color and look moist on the sides, bake for 10 to 20 minutes more. Turn off the oven and leave the éclairs in the oven to dry for 10 minutes more. Set on a cooling rack and cool completely before filling.
Make the lime powder:Use a Microplane to very finely grate two limes over a shallow plate. Microwave the zest in bursts of 10 seconds, using a fork to mix the zest around in between each cook. The zest should be dry to the touch after about 60 seconds. Let cool completely, then use a coffee grinder to turn it into a fine powder.
Assemble the éclairs: Transfer the coconut and lime pastry cream to a pastry bag fitted with a round tip, and transfer the kiwi curd to a second pastry bag fitted with a round tip as well. Using a serrated knife, saw the top third off of each éclair. Pipe a layer of kiwi curd to line the bottom of each éclair shell. Top with mounds of coconut and lime pastry cream.
Tuck cubes of green and golden kiwifruit in between the mounds of pastry cream. Close each éclair with its “lid,” gently setting it over the pastry cream without pressing. Top with more pastry cream and kiwifruit cubes, then finish with a sprinkle of lime powder.
Enjoy immediately, or refrigerate in airtight containers and eat within 24 hours.
Choux paste, instructions, and éclair concept: Marie Asselin.