Preheat oven to 425°F.: The first sensory cue is the warm, slightly sharp scent that fills the kitchen as the oven comes to temperature, signaling the right environment for rapid steam formation in the puff pastry . A hot oven ensures the layers rise quickly and separate, creating distinct flakiness. Avoid placing the tray in a lukewarm oven, which can make the pastry spread and become dense rather than airy. A common mistake is not allowing the oven to fully heat, so use an oven thermometer if you suspect your appliance runs cool.
Unfold puff pastry sheets and press layers on top of each other. Lightly press them together. Using a heart-shaped cookie cutter, cut out heart shapes in the dough. Discard excess dough.: You will feel the cool, supple texture of the dough under your fingers as you unfold it. Pressing two sheets together gives a pleasing thickness that holds filling well while still puffing up. When cutting, listen for a clean, paper like edge as the cutter slices; ragged cuts can seal layers together and inhibit lift. Keep any excess dough chilled to avoid it getting sticky, and avoid overhandling which warms the butter inside and reduces flakiness.
Remove the heart shapes and place them onto a parchment paper-lined baking sheet. Lightly brush with beaten egg and bake for 10 minutes.: As the tray goes into the oven you will notice a gentle, toasty aroma emerging around the seven to eight minute mark, with edges turning a rich golden color. The egg wash contributes to that glossy hue and helps create an appetizing crust. If you brush too heavily, the egg can drip and create dark spots; use a pastry brush and a gentle touch. A frequent error is overbaking; watch for even browning rather than deep mahogany, which indicates dryness.
Let cool, then cut heart dough pieces in half. Right before serving, fill with whipped cream and sliced strawberries.: Cooling is crucial so the warm interior does not melt the whipped cream . You should feel the shells firm up and hear a faint crackle when tapped, a sign they are properly crisp. When assembling, the contrast of cool cream and juicy strawberries against the still slightly warm pastry is delightful. Avoid slicing while piping the cream because residual heat can cause the filling to weep. A typical mistake is overfilling, which makes the hearts messy and hard to eat; aim for balance.
Sprinkle with sifted powdered sugar and enjoy.: The final step provides a soft, sweet note and a pretty visual finish; the powdered sugar dust will lightly catch on the textured surface. When you sprinkle it, do so from a height to create a gentle, snow like cover. If you do this too early, the sugar can absorb moisture and vanish, so wait until just before serving. One common oversight is using coarse sugar instead of sifted powdered sugar, which can look grainy rather than delicate.