Portobello mushroom burgers are no longer just a sad substitute for beef burgers; they are legitimately delicious choices on their own.
For charry grilled portobellos that wouldn't leak moisture and make the buns soggy, we decided to try scoring them, a technique that works well with oven-roasted mushrooms. It worked like a charm on the grill.
We lightly scored the mushrooms on the smooth, non-gill side in a crosshatch pattern. This helped expedite the release of moisture, which dripped out and evaporated on the grill, ensuring intense mushroom flavor and toasty, non-soggy buns. The crosshatching also allowed the mushrooms to absorb more marinade — a flavorful mix of olive oil, red wine vinegar and garlic.
Once they were cooked, we filled the portobello caps with a savory mixture of feta, sun-dried tomatoes, and roasted red peppers before stacking them on grilled buns with basil mayo, baby arugula and sweet grilled onions.
If your mushrooms are larger or smaller than 4-5 inches, you may need to adjust the cooking time accordingly. If the mushrooms absorb all the marinade, simply brush the onions with olive oil before grilling.