Make the BBQ sauce, if you don’t already have some on hand, to allow the flavors to infuse while you prepare the mushrooms (see notes below for homemade recipe).
Thinly slice the mushrooms. They should look shredded.
Heat the oil in a large skillet on medium heat.
When the oil is hot, add the mushrooms and onions and stir frequently until the mushrooms lose their water and the onions become translucent and soft, approximately 5 to 7 minutes. Depending on the size of the pan, you may need to cook the mushrooms and onions in two batches.
Turn up the heat to medium-high and add salt and pepper to taste. Cook until the onions caramelize and the edges of the mushrooms begin to crisp up, approximately 5 minutes.
When the mushrooms and onions are done cooking, add the BBQ sauce to the pan and stir until the mushrooms are completely coated in the sauce.
Bring the mixture to a boil on medium heat and then reduce the heat to a low simmer. Cook for 15 minutes, stirring frequently, until the sauce is thick and sticky.
Serve the mushrooms on the buns and top with the arugula, tomato and sliced pickles.
Notes
Gluten-Free option - use your favorite gluten-free buns or bread.Homemade BBQ Sauce Recipe (makes 2 cups):
1/2 teasp cornstarch
2 tbsp warm water
1 cup tomato sauce
2 tbsp tomato paste
3 cloves garlic or 3/4 teasp garlic powder
1/4 cup apple cider vinegar
2 tbsp dark molasses
1.5 teasp sea salt
1/4 cup + 1 tbsp coconut or dark brown sugar
1/2 teasp onion powder
1 teasp cumin
1 teasp paprika
1/2 teasp black pepper
1 teasp olive oil (optional)
Directions: In a small bowl, whisk the cornstarch and water together until smooth. You shouldn't see any lumps. set aside. Place the rest of the ingredients into a blender or food processor and blend on high until smooth and frothy. Pour the mixture into a small saucepan and bring to a boil. As soon as the sauce begins to boil, reduce the heat to a low simmer and cook for about 20 minutes. Stir frequently to prevent scorching. Slowly whisk the cornstarch into the sauce and keep whisking until the sauce thickens. Cook for 10 minutes, stirring frequently. Store in an airtight container in the refrigerator for up to 2 weeks.