My next step is always to look into the vegetable bin to see what I have to round out any meal. I found onions and a small handful of mushrooms so I decide to grill those for the burgers. I also found some avocados which just sliced and scooped for a nice side. Finally, I set up each plate with a bit of lettuce for our burgers.
When grilling onions I like to add them to the pan as a full slice - eventually I break them up but I feel that this allows the onions to get a nice even browning before they start softening. So I gently peeled a medium onion, and sliced nice rounds of onions less than a quarter inch each. I rinsed the mushrooms and sliced them thinly as well. With everything prepped; dishes set up, buns waiting to be toasted, patties defrosting and the mushrooms and onions sliced, I set my grill pan - which is an oval, Le Crueset skillet - on the burner at medium and add a tablespoon of olive oil.
When the oil started to gently smoke, I carefully added the rounds of onions doing my best not to break them into rings. Once the onions were placed, I let them brown on one side for a few minutes, gently flipped them and let them brown on the other side for bit. As the second side of each onion round was browning, I added the mushrooms (and a bit more oil because the pan seems a bit dry). I gently sauteed the onions and when they seemed to be cooking nicely I mix them with the browned onion - now breaking the onions into single rings. I moved this mixture of onions and mushrooms to the side of the pan and let the pan heat up a bit before adding the turkey patties.
As the second side of each turkey patty is browning, I put the hamburger buns in the toaster and a low setting just to get the bread warm - not too crisp. When the buns are warm, I bring them to the plate and add a turkey patty to each bottom bun followed by a layer of nicely grilled onions and mushrooms. It is up to everyone to personalize their own from there.