Preheat the oven to 425 degrees Fahrenheit and arrange a rack in the upper and lower thirds of the oven.
In a sauce pan over medium heat, add the milk, sugar, salt, butter, and water. Bring the mixture to a simmer using a wooden spoon to help the butter melt.
Once the mixture starts bubbling, add the flour all at once and stir with the wooden spoon. Once the flour has been incorporated, stir vigorously until everything comes together into a soft dough and there's a light film on the bottom of the sauce pan.
Continue to cook the dough over medium heat, vigorously beating the dough against the sides of the pan until the film on the bottom has reabsorbed into the bowl and the dough holds together in a ball, around 3 minutes
Transfer all of the dough into the bowl of your stand mixer with the paddle attachment. Let the dough sit for a minute or two then mix for 30 seconds to help cool the dough slightly.
On low-medium speed, add the eggs to the mixture one at a time. After each egg the mixture will look glossier and looser than before. After the fourth egg, check the consistency of the mixture. It needs to be thick enough to hold its shape but loose enough that when you pull the paddle out of the dough, it forms a V shape when it falls off the paddle. Add the fifth egg if needed to get the right consistency. See photos above for the "V" shape you're looking for.
Transfer the mixture to a piping bag with a 1-½" french star tip. Shake the bag a few times to get any air bubbles out and twist the bag to close.
Place the tip of the piping bag on the parchment paper at a 45 degree angle and without lifting the tip off of the paper, pipe a 4-5" long log. Twist the tip when you want to stop piping for a clean break. Dip your fingers in water and press the rough edge of the dough back in for a clean end. Repeat for the rest of your eclairs.
Dust the tops of your eclairs with a bit of powdered sugar or spray them with a bit of cooking spray like pam. This helps reduce cracking while baking
Place in the oven and reduce temperature to 375. Bake for 25 minutes. After 25 minutes poke a hole in the ends of all of the eclairs and bake for another 5 minutes
After 5 minutes, turn off the oven and leave eclairs inside to cool for 15-20 minutes. prop the oven door open with a wooden spoon to help the eclairs cool slowly.
Remove the eclairs from the oven and using a small paring knife, poke three holes in the bottom of each eclair to allow steam to escape as well as help with filling later. Let the eclairs cool completely on the baking tray.