Heat oven to 375℉/190℃.
Line 2 sheet pans with parchment paper. Set aside.
Sift flour. Set aside.
In a medium saucepan, combine milk, water, salt, sugar, and butter.
Bring to a boil over medium heat.
Remove from heat.
Using a wooden spoon, stir in flour.
Return to heat.
Cook, stirring continuously, until mixture cleans the sides of the pot, about 1 minute.
Transfer to stand mixer fitted with paddle attachment.
Beat in eggs, one at a time.
Continue beating until smooth and glossy.
Spoon into piping bag.
Snip end of bag to a ½" opening.
Pipe into ½" rounds onto prepared pans, about 26 per pan.
Tap down peaks with a wet finger.
Bake for 10 minutes.
Immediately reduce temperature to 350℉. (Do NOT open oven door.)
Bake 20-25 minutes, until golden brown on the outside and dry in the center.
Allow to cool on pans.