Preheat oven to 425 and line baking sheet(s) with parchment paper. This recipe makes about 24 puffs.
Add water, milk, butter, sugar, and salt to a pan on the stove and mix over medium to high heat. Bring to a boil and then remove from heat.
Add flour and quickly stir into mixture. It really starts to form more a dough at this point.
Return pan back to the stove top on medium heat and stir constantly for a few minutes, cooking until mixture pulls away from the pan and a film forms on the bottom of the pan. This happened pretty quickly for me.
Transfer the dough to a mixer or bowl and beat on low speed for 3-4 minutes until cooled.
Add eggs one at a time and beat on medium speed until each is fully mixed in. Mix until shiny and almost ribbon like.
Place dough in a pastry bag with a round tip. Pipe round circles spaced at least 1 inch apart on parchment paper. Since this was the first time I did this, I guessed a little. The puffs that came out the best were the ones that I did a second layer on top so they were a little higher and could rise (see photo). Try not to pull up and leave a peak, but you can smooth down with your finger if needed.
Place one baking sheet at a time in the oven and bake for 15 minutes.
Lower oven temperature to 375 and continue baking for another 5-10 minutes, until golden and airy. Keep an eye on them because they brown quickly!
Remove from oven and transfer to a wire rack to cool.
Repeat steps 8-10 for the other baking sheet and make sure your oven heats back up to 425 to before the second pan goes in.