• 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
1. Preheat 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.
2. Add 1 egg and beat hard 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.
3. In a small bowl, combine egg yolk and milk; mix well and brush over dough.
4. Bake 25 to 30 minutes, or until golden. Remove to a wire rack to cool completely.
5. In a large bowl, beat cream with an electric beater on medium speed until soft peaks form. Add 1/3 cup confectioners’ sugar and vanilla and beat until stiff peaks form.
6. Cut top third off each cooled 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.