Preheat oven to 375°F (190°C). Line 2 to 3 baking sheets with parchment paper.
Using a permanent marker and a 2-inch round cutter as a guide, draw circles at least 1½ inches apart on another sheet of parchment paper; slide template under parchment on a prepared pan.
In a medium saucepan, bring butter, ½ cup (120 grams) water, milk, sugar, and salt to a rolling boil over medium-high heat. Using a wooden spoon, stir in flour. Cook, stirring constantly, until a skin forms on bottom of pan and mixture pulls away from sides of pan and forms a ball, 1 to 2 minutes. Transfer mixture to the bowl of a stand mixer fitted with the paddle attachment; beat at low speed until dough cools slightly, 30 seconds to 1 minute. Add eggs, one at a time, beating until combined. (Batter will be shiny and will slowly move back together when a spatula is dragged through it.)
Transfer batter to a large pastry bag fitted with a ½-inch round piping tip (Wilton 1A). Place piping tip in center of a drawn circle. Hold tip perpendicular ½ inch above parchment paper. Holding tip stationary the entire time, apply even pressure until batter reaches edges of drawn circle. Stop applying pressure, and move tip in a quick circular motion as you lift away to help prevent a point from forming on top. Repeat with remaining batter until pan is full. Wet your finger with water, and press down any points to create a smooth top, if necessary. Slide template out from under piped batter, and place under parchment on other prepared pans; pipe remaining batter. Top each piped choux puff with a frozen Craquelin Cookie right before baking.
Bake in batches for 10 minutes. Rotate pan, and bake until fully puffed and deep golden brown, 10 to 15 minutes more. Let choux puffs cool completely on pans.
Using a serrated knife, cut off top quarter of each cooled choux puff; set aside. Using a skewer or wooden pick, clear any dough strands. Place Diplomat Cream in a large pastry bag fitted with a ½-inch open star piping tip (Wilton 1M). Pipe cream into each puff, and place cut top piece on top of piped cream. Serve immediately, or refrigerate until ready to serve. Best served same day.
Recipe by Bake from Scratch at https://bakefromscratch.com/july-pate-choux-two-ways/