Preheat oven to 400ºF. Line a baking tray with parchment paper. Spread sweet potatoes in a single layer on the tray. Drizzle with olive oil and sprinkle with salt. Place tray in oven and roast for about 20 minutes, or until potatoes are tender and easily pierced with a fork. Remove tray from oven and empty into a serving bowl. Cover and set aside.

While the sweet potatoes are roasting, set a pan on medium-high heat on the stove. Heat a tablespoon or two of olive oil. Add sliced mushrooms and a good sprinkle of salt. Cook for about 15 minutes, while stirring occasionally, until mushrooms are dark brown and most of the liquid that was released has evaporated. Empty mushrooms into a serving bowl. Cover and set aside. Do not wash the pan.

Set the same pan used for the mushrooms over medium-high heat. Heat a tablespoon or two of olive oil for about a minute. Add chopped onion and a good sprinkle of salt. Cook until onion has softened and has turned translucent, about 8 minutes. Add vinegar, garlic, cumin, chili powder, oregano, and chipotle. Stir and cook until garlic and spices have become fragrant, another 2 to 3 minutes. Add lentils and stir to combine. Cook for about 10 minutes more. Taste and adjust seasonings, then empty into a serving bowl. Cover and set aside. Do not wash the pan.

Set the unwashed pan on the stove over medium-high heat. Heat olive oil for a minute. Add greens and garlic. Stir to mix. Cook until greens turn brighter and begin to wilt, about 3 to 5 minutes. Remove pan from heat and sprinkle greens with a little salt. Empty greens into a serving bowl and cover.

Set all bowls on the table, and place tacos on a plate. Let each person assemble and garnish their own tacos.