Sauté the mushrooms: Slice the mushrooms into 1/4-inch slices. Mince the garlic. In a large skillet, heat 2 tablespoons olive oil over medium high heat. Add the mushrooms and cook 5 to 6 minutes, stirring occasionally, until softened. Lower the heat to medium and stir in the additional 1 tablespoon olive oil, garlic, cumin seed, cumin, smoked paprika, kosher salt and black pepper. Cook 1 to 2 minutes until fragrant, then turn off the heat and stir in the lime juice.
Heat the beans: Heat the refried beans in a small saucepan until warm. Taste and add a few pinches of kosher salt if necessary.
Make the quick slaw: Shred the red cabbage. Place it in a bowl and add the juice of 1 lime quarter and 2 pinches of kosher salt. Dice the avocado, if using.
Warm the tortillas: Warm and char the tortillas by placing them on an open gas flame on medium for a few seconds per side, flipping with tongs, until they are slightly blackened and warm or warm in a pan on your stove top.
Assemble the tacos: Add a generous spoonful of refried beans, a small handful of mushrooms, slaw, avocado, pico de gallo, and vean cheese crumbles, if using.