1 cup water
1/4 cup (1/2 stick) butter, softened
1/4 teaspoon salt
1 cup all-purpose flour
4 eggs, at room temperature
1 egg yolk
2 tablespoons milk
2 cups (1 pint) heavy cream
1/3 cup confectioners' sugar, plus extra for sprinkling
2 teaspoons vanilla extract
DirectionsPreheat oven to 400 degrees F. In a medium saucepan over medium-high heat, bring water, butter, and salt to a boil. Add flour all at once and stir quickly until mixture forms a ball; remove from heat. Add 1 egg and mix well with a wooden spoon to blend. Add remaining whole eggs one at a time, beating well after each addition; each egg must be completely blended in before the next egg is added. As you beat mixture, it will change from an almost-curdled to a smooth appearance. When it is smooth, spoon 12 mounds of dough onto a large rimmed baking sheet.
In a small bowl, combine egg yolk and milk; mix well and brush over dough.
Bake 25 to 30 minutes, or until golden. Remove to a wire rack to cool completely.
In a large bowl with an electric mixer on medium speed, beat heavy cream until soft peaks form. Add 1/3 cup confectioners' sugar and the vanilla and beat until stiff peaks form. Cut top third off each pastry puff and fill with equal amounts of whipped cream mixture. Replace tops and sprinkle with confectioners' sugar. Serve immediately, or cover and chill until ready to serve.
For a sure way to get perfect whipped cream, chill the bowl and beaters before whipping the cream, and make sure not to overbeat it.