Prepare the oven and baking sheet. Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper.
Cut the pastry rings. Roll the puff pastry thinly on a lightly floured surface. Cut circles with an 8 cm cutter, then remove the center of each circle with a 4 cm cutter to create rings.
Stack the rings. Lightly brush one ring with beaten egg and place a second ring directly on top, aligning the edges. Repeat with the remaining pastry rings.
Brush and bake. Arrange the stacked rings on the prepared baking sheet, leaving space between them. Lightly brush the tops with egg, avoiding the cut sides. Bake for 12–14 minutes, or until puffed, golden, and baked through.
Cool completely. Remove the pastries from the oven and let them cool completely before filling.
Prepare the vanilla cream. Pour the cold milk into a mixing bowl. Add the vanilla cream mix and powdered sugar. Beat with an electric mixer until smooth, thick, and suitable for piping.
Fill the pastries. Fit a piping bag with a large tip and spoon in the cream. Place the cooled pastries on a serving plate. Pipe cream into the center of each ring, building a decorative swirl above the rim.
Decorate and serve. Top with your chosen fruit and lightly dust with powdered sugar just before serving.