Making these Raspberry Mille-Feuille Cookies is a rewarding process, and with a few simple steps, you’ll be enjoying these delightful treats in no time. Follow these instructions carefully to achieve perfect, flaky, and flavorful cookies.

1. Prepare the Puff Pastry: Preheat your oven to 400°F (200°C). Line two baking sheets with parchment paper. Gently unfold the thawed puff pastry sheet on a lightly floured surface. If your puff pastry is very thick, you might want to gently roll it out slightly to an even thickness of about ⅛ inch. This ensures even baking and crispiness. Using a sharp knife or a pizza cutter, cut the puff pastry sheet into even rectangles. Aim for approximately 2-inch by 3-inch rectangles. You should get about 18-24 rectangles depending on the size of your puff pastry sheet. The more uniform your rectangles, the more consistent your cookies will be.
2. Bake the Puff Pastry Layers: Place the puff pastry rectangles on the prepared baking sheets, leaving some space between each cookie to allow for even baking and expansion. Prick each rectangle several times with a fork. This is crucial to prevent the puff pastry from puffing up too much and becoming too thick in the center. Pricking helps release steam and encourages the pastry to bake flat and flaky. Lightly dust the puff pastry rectangles with powdered sugar. This will caramelize as they bake, adding a touch of sweetness and a beautiful golden-brown color. Bake for 12-15 minutes, or until the puff pastry is golden brown and puffed. Keep a close eye on them, as puff pastry can burn quickly. If they start to brown too quickly, reduce the oven temperature slightly. Once baked, remove the baking sheets from the oven and let the puff pastry layers cool completely on wire racks. This is essential for them to crisp up properly. Don’t try to assemble them while they are still warm, as the filling will melt and the pastry might become soggy.
3. Prepare the Raspberry Filling: While the puff pastry is cooling, prepare the raspberry cream filling. In a large bowl, combine the softened mascarpone cheese, cold heavy cream, vanilla extract, and powdered sugar. Using an electric mixer (hand mixer or stand mixer), beat on medium-high speed until stiff peaks form. Be careful not to overbeat, as this can cause the cream to curdle. You want a firm, yet smooth and creamy texture that will hold its shape when piped or spread. Gently fold in the raspberry jam and half of the fresh raspberries (roughly chopped). Folding gently ensures that the cream remains light and airy and the raspberries are evenly distributed without being crushed too much. The chopped raspberries add texture and intense raspberry flavor throughout the cream.
4. Assemble the Mille-Feuille Cookies: Once the puff pastry layers are completely cool, it’s time to assemble your Raspberry Mille-Feuille Cookies. Place one puff pastry rectangle on a serving plate or cutting board. Spoon or pipe a generous layer of the raspberry cream filling onto the puff pastry. You can use a piping bag for a more elegant presentation, or simply spread the filling evenly with a spatula or spoon. Place another puff pastry rectangle on top of the cream filling. Gently press down to secure it in place. Repeat with another layer of raspberry cream filling and top with the final puff pastry rectangle. You should have three layers of puff pastry and two layers of raspberry cream filling for each cookie.
5. Garnish and Serve: Dust the top of each assembled Mille-Feuille cookie generously with powdered sugar. This adds a final touch of sweetness and visual appeal. Arrange the remaining fresh raspberries on top of the powdered sugar dusting for a beautiful and fresh garnish. The vibrant red raspberries against the white powdered sugar and golden pastry create a stunning presentation. Serve immediately for the best texture and flavor. These cookies are best enjoyed soon after assembly, as the puff pastry can soften slightly over time due to the moisture from the filling. However, they can be stored in the refrigerator for a few hours if needed, but the pastry will lose some of its crispness.