Directions
<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Start by preheating your oven to 175°C (350°F) and line two baking sheets with parchment paper. Proper preheating ensures your cookies bake evenly and develop that perfect texture – crisp edges with slightly chewy centers.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>In a medium bowl, whisk together the gluten-free flour blend, cocoa powder, baking soda, and salt until thoroughly combined. This thorough mixing is especially important with gluten-free flours to ensure even distribution of leavening agents and prevent any bitter pockets of baking soda.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>In the bowl of your stand mixer fitted with the paddle attachment, cream the softened butter, granulated sugar, and brown sugar on medium speed for about 3-4 minutes until light and fluffy. This extended creaming incorporates air into the mixture, which helps create structure in gluten-free cookies that might otherwise be dense.</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>Add the egg and vanilla extract to the butter mixture, beating well after each addition until fully incorporated and the mixture looks smooth and glossy. The egg provides crucial structure and moisture to bind your gluten-free ingredients together.</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>With the mixer on low speed, gradually add the dry ingredients to the wet ingredients, mixing just until combined. Overmixing can make your cookies tough, even without gluten. The dough will be somewhat thick – that's exactly what we want!</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>Fold in the chocolate chunks by hand using a rubber spatula. This gentle treatment preserves those beautiful chunks of chocolate that will create pockets of melty goodness in your finished cookies.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>Using your cookie scoop, portion the dough into 24 equal balls (about 30g each) and place them on the prepared baking sheets, leaving at least 5cm (2 inches) between cookies as they will spread. For perfectly uniform sandwich cookies, weigh each portion if possible.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>Gently flatten each dough ball slightly with your palm – just enough to give them a head start on spreading evenly. If using, sprinkle a tiny amount of flaky sea salt on top of each cookie to enhance the chocolate flavor.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>Bake in the preheated oven for 10-12 minutes, rotating the pan halfway through baking time. The cookies are done when the edges are set but the centers still appear slightly soft – they'll continue cooking on the hot baking sheet. For gluten-free cookies, it's better to slightly underbake than overbake to maintain chewiness.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>Allow the cookies to cool on the baking sheets for 5 minutes, during which time they'll firm up enough to move. Then transfer them to wire racks to cool completely before filling. Patience is key – warm cookies will cause your filling to melt!</li><li class="MethodStepper"><h4 class="step-title">Step 11</h4>While the cookies cool, prepare the filling. In your cleaned stand mixer bowl with paddle attachment, beat the softened butter on medium speed until completely smooth, about 2 minutes. This initial beating ensures no lumps in your filling.</li><li class="MethodStepper"><h4 class="step-title">Step 12</h4>Gradually add the sifted powdered sugar, milk, vanilla extract, and salt to the butter. Start mixing on low speed to prevent a sugar cloud, then increase to medium-high and beat for 3-4 minutes until light, fluffy, and silky smooth. The filling should hold its shape but be soft enough to pipe or spread.</li><li class="MethodStepper"><h4 class="step-title">Step 13</h4>Turn half of the completely cooled cookies upside down and pipe or spoon about 1-2 tablespoons of filling onto the flat side of each cookie. Don't spread the filling all the way to the edge – when you place the second cookie on top, the pressure will push the filling outward.</li><li class="MethodStepper"><h4 class="step-title">Step 14</h4>Gently press the remaining cookies on top of the filling, flat side down, to create sandwiches. Apply just enough pressure to spread the filling to the edges without squeezing it out completely.</li><li class="MethodStepper"><h4 class="step-title">Step 15</h4>Allow the assembled sandwich cookies to rest for about 30 minutes before serving to let the filling set. This rest time helps the flavors meld together and creates that perfect cookie-to-filling bond. Store in an airtight container at room temperature for up to 3 days, or refrigerate for up to a week (but bring to room temperature before serving for the best texture and flavor).</li></ol>