In a medium saucepan, heat milk over medium low heat, stirring occasionally, until steaming (do not boil).
In a medium bowl, whisk together egg yolks, sugar, cornstarch, and salt. Whisking constantly, slowly add warm milk mixture into egg yolk mixture. Return mixture to saucepan and bring to a boil over medium-low heat, whisking constantly. Cook, whisking constantly, until cornstarch flavor has cooked out and custard has thickened, 2 to 3 minutes. Stir in vanilla extract and butter. Remove from heat and strain through a fine-mesh sieve into a medium heatproof bowl. Cover with a piece of plastic wrap, pressing wrap directly onto surface to prevent a skin from forming. Refrigerate until completely cooled, about 4 hours.
In the bowl to a stand mixer fitted with a whisk attachment, whisk cold cream and rose water until stiff peaks form, 3 to 4 minutes.
Transfer chilled pastry cream to a large bowl and whisk until smooth. Fold in whipped cream in three additions. Use immediately or refrigerate until ready to use. Best used same day.
Recipe by Victoria at https://victoriamag.com/rose-choux-puffs/