01 -
In a medium bowl, whisk together the egg yolks, granulated sugar, cornstarch, and lemon zest until the ingredients are fully combined and the mixture becomes smooth.
02 -
In a medium saucepan, combine whole milk and heavy cream. Warm over medium heat until the mixture begins to steam and tiny bubbles form at the edges, avoiding any boiling.
03 -
Gradually drizzle the warm milk and cream into the egg mixture, whisking constantly to prevent curdling. Add a few tablespoons at a time, whisking well after each addition until fully incorporated.
04 -
Pour the mixture back into the saucepan and cook over medium heat, whisking continuously, until thickened and bubbling (about 3 to 5 minutes). The consistency should match that of a pudding.
05 -
Remove from heat. Whisk in the lemon juice, unsalted butter, and vanilla extract until completely blended. Strain the pastry cream through a fine mesh sieve into a clean bowl to ensure a smooth texture. Cover with plastic wrap, pressing it directly onto the surface. Chill in the refrigerator for 1 to 2 hours, or until set.
06 -
Preheat oven to 375°F (190°C). Line a large baking tray with parchment paper. Unfold the thawed puff pastry sheet on parchment and cut it into 6 equal rectangles using a sharp knife or pizza cutter.
07 -
Space the pastry rectangles 2 inches apart on the prepared tray. Score a smaller rectangle inside each piece about 1/4 inch from the edge—be careful not to cut through completely. Lightly brush the tops with heavy cream and sprinkle raw sugar evenly over each.
08 -
Bake on the center rack for 25 to 30 minutes or until pastries are puffed and golden brown.
09 -
While still warm, gently cut along the scored lines and press down or remove the centers to make wells for the filling. Allow shells to cool completely.
10 -
Transfer the chilled lemon pastry cream to a piping bag. Pipe the cream into the cooled pastry shells. Top generously with fresh blueberries and dust lightly with powdered sugar. Serve immediately.