FOR THE ECLAIRS
Preheat oven to 425F.
Line two baking sheets with silicone baking mats or parchment paper; set aside.
Combine milk, water, butter, sugar and salt in a medium heavy-bottomed saucepan; set over high heat and bring to a rapid boil.
Add the flour, lower heat to medium-low and immediately start stirring vigorously with a wooden spoon or heavy whisk. The dough will come together, and a crust will form on the bottom of the pan.
Keep stirring for another minute or two, or until dough is dry and smooth.
Turn the dough into the bowl of a stand mixer fitted with the paddle attachment or into a bowl you can use to mix with a hand mixer or a wooden spoon and elbow grease.
Let dough sit for 1 minute; add the eggs one by one and beat until the dough is thick and shiny.
Using about 1 tablespoon dough for each puff, drop the dough from a spoon onto the previously prepared sheets, leaving 2 inches of space between the mounds of dough.
Lower oven temperature to 375 and bake for 12 minutes, then rotate the pans from front to back and top to bottom; continue to bake for another 12 to 15 minutes, or until golden and puffed.
Remove from oven and let cool on baking sheets.
In the meantime, prepare the Filling.
Add Nutella, cream cheese, powdered sugar, and vanilla to the bowl of a stand mixer fitted with the paddle attachment; beat on medium-high speed until thoroughly combined.
With the mixer running, slowly add the cream, 1 tablespoon at a time, until filling combines and desired consistency is achieved.
Using a serrated knife and a gentle sawing motion, you can simply cut off the top quarter or third of each puff, fill the puffs with the Nutella Filling, and top them with the caps. Set aside.
Make the Glaze
Combine all ingredients in a medium bowl; whisk gently to combine. If the glaze seems too thick, add more milk; if too thin, add more sugar.
Using a small icing spatula or a butter knife, glaze the tops of the eclairs, then settle the tops gently of the filled bases.
Refrigerate the eclairs for at least 1 hour (or up to 8 hours) before serving.
Adapted from Around My French Table by Dorie Greenspan