Ingredients

• 2 1/4 cups whole milk
• 1/4 teaspoon salt
• 4 large egg yolks
• 2/3 cup sugar
• 2 tablespoons all-purpose flour
• 2 tablespoons cornstarch
• 2 tablespoons unsalted butter, cut into pieces
• 3 tablespoons grappa
• 2/3 cup chilled heavy cream
• 1 1/2 lb rhubarb stalks, cut diagonally into 1 1/4-inch pieces
• 1 cup water
• 1/3 cup sugar
• 2 tablespoons grappa
• 1 (17 1/4-oz) package frozen puff pastry sheets, thawed
• Garnish: confectioners sugar

Instructions

1. Bring 2 cups milk with salt to a boil in a 3-quart heavy saucepan. Meanwhile, whisk together yolks, sugar, flour, cornstarch, and remaining 1/4 cup milk in a bowl. Add one third of hot milk to yolk mixture in a slow stream, whisking, then add to milk remaining in saucepan, whisking.
2. Bring custard to a boil over moderate heat, whisking, and boil, whisking, 2 minutes. Remove from heat and stir in butter until melted, then stir in grappa. Transfer custard to a bowl and chill, its surface covered with wax paper, until cold, at least 1 hour.
3. Cook rhubarb while custard chills: Simmer rhubarb, water, sugar, and grappa in cleaned 3-quart heavy saucepan, uncovered, stirring gently once or twice, until rhubarb is tender but not falling apart, about 4 minutes. Set pan in a bowl of ice and cold water and let stand 2 minutes to stop cooking. Slowly pour rhubarb mixture into a sieve set over a bowl. Return syrup to saucepan, reserving rhubarb, and boil until reduced to about 1/2 cup, about 10 minutes. Keep rhubarb and syrup, covered, at room temperature until ready to use.
4. Simmer rhubarb, water, sugar, and grappa in cleaned 3-quart heavy saucepan, uncovered, stirring gently once or twice, until rhubarb is tender but not falling apart, about 4 minutes. Set pan in a bowl of ice and cold water and let stand 2 minutes to stop cooking.
5. Slowly pour rhubarb mixture into a sieve set over a bowl. Return syrup to saucepan, reserving rhubarb, and boil until reduced to about 1/2 cup, about 10 minutes. Keep rhubarb and syrup, covered, at room temperature until ready to use.
6. Prepare pastry while rhubarb cooks: Preheat oven to 400°F. Unfold 1 puff pastry sheet and gently roll out into a 14-inch square with a rolling pin on a lightly floured surface. Transfer to a buttered large baking sheet and prick all over with a fork. Repeat with remaining sheet. Bake in upper and lower thirds of oven, switching position of sheets halfway through baking, until pastry is puffed and golden, about 15 minutes total. Cool on baking sheets on racks. Trim edges of pastry with a large serrated knife. Cut each sheet into 12 (3-inch) squares and break pastry scraps into small shards.
7. Preheat oven to 400°F.
8. Unfold 1 puff pastry sheet and gently roll out into a 14-inch square with a rolling pin on a lightly floured surface. Transfer to a buttered large baking sheet and prick all over with a fork. Repeat with remaining sheet.
9. Bake in upper and lower thirds of oven, switching position of sheets halfway through baking, until pastry is puffed and golden, about 15 minutes total. Cool on baking sheets on racks.
10. Trim edges of pastry with a large serrated knife. Cut each sheet into 12 (3-inch) squares and break pastry scraps into small shards.
11. Assemble millefoglie: Beat cream (for custard) in a bowl with an electric mixer until it just holds soft peaks. Whisk custard to loosen, then fold in whipped cream gently but thoroughly. Dollop 2 rounded tablespoons of grappa cream on each of 8 dessert plates and top with half of rhubarb. Cover cream and rhubarb on each plate with a pastry square. Make another layer with remaining grappa cream, rhubarb, and pastry squares, then top with pastry shards. Sift confectioners sugar evenly over each serving and drizzle with syrup.
12. Beat cream (for custard) in a bowl with an electric mixer until it just holds soft peaks. Whisk custard to loosen, then fold in whipped cream gently but thoroughly.
13. Dollop 2 rounded tablespoons of grappa cream on each of 8 dessert plates and top with half of rhubarb. Cover cream and rhubarb on each plate with a pastry square. Make another layer with remaining grappa cream, rhubarb, and pastry squares, then top with pastry shards. Sift confectioners sugar evenly over each serving and drizzle with syrup.