- reheat oven to 300 degrees. While the oven is heating, begin charring the wood chips in a pan over high heat until they begin to smoke and almost catch on fire (be sure to turn your hood vents on for this step). While the wood chips are charring on the stove, break mushrooms into bite-size pieces and set aside in a large mixing bowl.
- For the rajas, toss onions, peppers, and mushrooms with the olive oil and salt and spread onto a sheet pan. Place sheet pan on top rack of oven and place pan of smoking wood chips on bottom rack. Roast for 20 minutes. (You just want to par-cook the mushrooms and let them absorb as much of the smoke as possible.)
- While the mushrooms are cooking, roast the garlic cloves in a dry sauté pan over medium heat until they are soft and cooked throughout, about 5 minutes. Smash garlic with a knife, mince until almost puréed, and fold into sour cream with a pinch of salt. Set aside.
- Heat the tortillas in a sauté pan until hot and wrap in a towel to steam while you sear the mushrooms and rajas in a separate sauté pan to caramelize the mushrooms, adjusting seasoning as needed. Serve roasted mushroom-poblano raja tacos with garlic crema, Cotija, and cilantro.