While the onions are cooking, prep the mushrooms and the burgers.
Mix the seasoning for the burgers. Form 4 patties and season them with the seasoning,
Heat nonstick or cast-iron skillet over medium heat. Add olive oil and heat. Next add in mushrooms, salt, and garlic. Cook, stirring occasionally until the mushrooms are tender and have shrunk. Mine took about 5 minutes.I prefer to use my mushrooms right away. They can be stored in an airtight container for up to 2 days if you need to.
Now, heat your grill or cast-iron skillet as I did. You will want it pretty hot before you add the burgers.
Once it is heated, add the burgers. Cook for about 3-6 minutes per side, depending on how you take your burger.
Next, assemble the burgers. Add the burger to your bun, then the mushrooms, onions, and swiss cheese.
Last, slather with the aioli!
You are done. Sit back and enjoy. You deserve it!