Directions
<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Begin by preparing your brioche bun dough. In the bowl of your stand mixer, combine the warm milk (around 43°C/110°F - warm but not hot to touch) with the yeast and 1 tablespoon of the sugar. Let it sit for 5-10 minutes until foamy and activated. This foam indicates your yeast is alive and ready to help create that perfect light texture.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>Add the remaining sugar, 2 eggs, flour, and salt to the mixer bowl. Using the dough hook attachment, mix on low speed until roughly combined, then increase to medium speed and knead for about 5 minutes until the dough comes together but still appears somewhat shaggy.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>With the mixer running on medium speed, add the softened butter one tablespoon at a time, waiting until each addition is fully incorporated before adding more. This gradual addition prevents the emulsion from breaking and ensures a silky-smooth dough. Continue kneading for 8-10 minutes until the dough is glossy, elastic, and passes the windowpane test (when stretched, it becomes thin enough to see light through without tearing).</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>Transfer the dough to a lightly oiled bowl, cover with plastic wrap or a damp cloth, and let rise in a warm place until doubled in size, about 1-2 hours. The high butter and egg content means this enriched dough rises more slowly than standard bread dough, so be patient.</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>While the dough is rising, prepare your portobello mushrooms. Gently clean the caps with a damp paper towel (never submerge mushrooms in water as they absorb moisture like sponges). Remove the stems and use a spoon to carefully scrape out the dark gills underneath - this prevents your burger from becoming soggy and discolored.</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>In a shallow dish, whisk together the balsamic vinegar, olive oil, minced garlic, thyme leaves, honey, salt and pepper. Place the mushroom caps in the marinade, gill-side down first, then flip to coat both sides. Allow to marinate for at least 20 minutes, turning occasionally. The acidic balsamic helps tenderize the mushrooms while infusing them with flavor.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>After the dough has doubled, punch it down gently to release air bubbles. Turn out onto a lightly floured surface and divide into 8 equal pieces (about 100-110g each). For burger buns, shape each piece into a tight ball by pulling the edges toward the center and pinching them together, then rolling between your palms on the countertop to create tension on the surface. Place the shaped buns on parchment-lined baking sheets, leaving at least 5cm between each.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>Cover the shaped buns loosely and let them proof for another 45-60 minutes until they've puffed up significantly. Meanwhile, preheat your oven to 190°C (375°F) and prepare the egg wash by beating the remaining egg with 1 tablespoon of water.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>Once the buns have proofed, gently brush them with egg wash (be careful not to deflate them) and sprinkle with sesame seeds. Bake for 15-18 minutes until golden brown and an internal temperature reaches 88-93°C (190-200°F). Transfer to a wire rack to cool completely.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>While the buns are cooling, increase oven temperature to 200°C (400°F). Remove the mushrooms from the marinade (reserve the marinade) and place them gill-side up on a parchment-lined baking sheet. Roast for about 15 minutes, then flip, brush with reserved marinade, and roast another 5-10 minutes until the mushrooms are tender and juicy but not soggy. Baking rather than grilling helps control moisture release and creates a meaty texture.</li><li class="MethodStepper"><h4 class="step-title">Step 11</h4>In the last few minutes of roasting, place a slice of cheese on each mushroom and return to the oven until melted. Meanwhile, prepare the garlic aioli by mixing all aioli ingredients in a small bowl until well combined.</li><li class="MethodStepper"><h4 class="step-title">Step 12</h4>To assemble your burgers, slice the cooled brioche buns horizontally with a serrated knife. Spread garlic aioli on the bottom half, add lettuce, then place the cheese-topped portobello (allow any excess moisture to drain off first). Top with tomato, red onion if using, more aioli on the top bun, and serve immediately. The warm mushroom against the cool vegetables and creamy aioli creates a delightful temperature contrast that elevates the burger experience.</li></ol>