Directions
<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Make the strawberry filling first so it has time to cool completely. In a medium saucepan, combine the chopped strawberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the strawberries break down and the mixture thickens, about 15-20 minutes. The jam should coat the back of a spoon and leave a clear path when you run your finger through it. Remove from heat, stir in the vanilla extract, and transfer to a heat-proof container. Refrigerate until completely cool, at least 1 hour.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>For the cookie dough, whisk together the flour, cornstarch, and salt in a medium bowl. The cornstarch is crucial here as it helps create that melt-in-your-mouth tender texture that's characteristic of shortbread. Set aside.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>In the bowl of your stand mixer fitted with the paddle attachment, beat the butter and powdered sugar on medium speed until light and fluffy, about 3 minutes. This extended creaming incorporates air into the mixture, ensuring your cookies will have a light texture. Add the vanilla extract and egg yolk, beating until combined and scraping down the sides of the bowl as needed.</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>With the mixer on low speed, gradually add the flour mixture until just combined. Be careful not to overmix, which can develop the gluten and make your cookies tough rather than tender. The dough will be soft but not sticky.</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>Divide the dough in half and form each portion into a disk. Wrap in plastic wrap and refrigerate for at least 1 hour, or up to 2 days. Chilling the dough allows the flour to hydrate fully and prevents the cookies from spreading too much during baking.</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>When ready to bake, preheat your oven to 180°C (350°F) and line two baking sheets with parchment paper. Remove one disk of dough from the refrigerator and let stand for about 5-10 minutes to slightly soften.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>On a lightly floured surface, roll the dough to about 0.5cm (1/4 inch) thickness. Using your cookie cutter, cut out as many rounds as possible and transfer to the prepared baking sheets, spacing them about 2.5cm (1 inch) apart. Gather the scraps, reroll, and cut out more cookies. Repeat with the second disk of dough.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>Sprinkle the tops of the cookies with granulated sugar for a lovely sparkle and crunch. Bake for 10-12 minutes, until the edges are just barely turning golden. Don't overbake – the cookies should not brown much to maintain their tender texture. Cool on the baking sheets for 5 minutes, then transfer to wire racks to cool completely.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>While the cookies cool, prepare the vanilla cream filling. In the bowl of your stand mixer fitted with the paddle attachment, beat the softened butter until creamy. Gradually add the sifted powdered sugar, mixing on low speed until incorporated, then increase to medium-high and beat until light and fluffy, about 3 minutes.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>Add the softened cream cheese, vanilla extract, and pinch of salt. Beat on medium speed until smooth and well combined, about 2 minutes. Be careful not to overmix once the cream cheese is added, as it can become too soft. If the filling seems too soft to pipe, refrigerate for 15-20 minutes to firm up slightly.</li><li class="MethodStepper"><h4 class="step-title">Step 11</h4>To assemble the cookies, turn half of the cooled cookies upside down. Pipe or spread about 1 teaspoon of the strawberry filling in the center of each cookie. Pipe or spread a ring of vanilla cream around the strawberry filling, leaving a small border around the edge (this prevents the filling from squeezing out when you sandwich the cookies). Top with the remaining cookies, pressing gently to adhere.</li><li class="MethodStepper"><h4 class="step-title">Step 12</h4>Refrigerate the assembled sandwich cookies for at least 30 minutes to allow the fillings to set up. This makes them easier to handle and helps the flavors meld together. Bring to room temperature for about 15 minutes before serving for the best texture and flavor experience. The cookies can be stored in an airtight container in the refrigerator for up to 3 days.</li></ol>