To make the puffs:

Cup of Yum
1. Preheat oven to 400 degrees. Line 2 baking sheets with parchment paper or silicone mats. In a large saucepan over medium heat, bring water, butter and salt to boil. Remove from heat, add flour, and stir constantly until a smooth ball forms. 
2. Let stand for 5 minutes. Add eggs, one at a time, beating well after each addition. Continue beating until mixture is smooth and shiny.
3. Using a 1/4 cup measuring cup or large portion scoop, drop 5 balls of dough on to each baking sheet, four towards the corners and one in the middle but at least 3 inches apart (I use the OXO large cookie scoop, a size 20 portioner, and do heaping scoops).
4. To make the egg wash, whisk together egg yolk and milk. Brush lightly over puffs. Bake 30-35 minutes or until golden brown. Remove to wire racks. Immediately cut a slit in each for steam to escape. Cool completely.

To assemble the puffs:

1. While the puffs are cooling, chill a metal mixing bowl and metal whisk in freezer for 10 to 15 minutes.
2. Combine cream, powdered sugar, and vanilla in chilled mixing bowl and beat until stiff peaks form, about 6 to 8 minutes.
3. Split cream puffs and discard soft dough from inside. Fill the cream puffs just before serving. Dust with powdered sugar.