Preheat grill, medium heat. Toss the onions and peppers together with a couple of tablespoons of olive oil, oregano, chili pepper, cumin and a good sprinkle of salt and pepper. Place in a grill pan or a double-layer of foil and close the cover. Cook, stirring occasionally, for about 10 minutes, or until the vegetables have begun to soften and brown. Add the mushroom strips and gently toss to coat, being careful not to break the mushrooms. Cook for another 10 minutes, until the mushrooms are no longer white inside and all the vegetables are soft.

While the vegetables are cooking, place two sheets of foil on a flat surface. Drizzle a tablespoon or two of olive oil on the foil. Empty the hash browns onto the foil and sprinkle with salt and pepper. Place another pice of foil over the top and seal the edges. Place the foil package on the grill and cook for about 15 to 20 minutes. Pierce the top of the foil after about 10 minutes to check. Potatoes should be browning on the bottom.

To blanch the collard leaves, set a large pot of salted water on the stove on medium-high heat. Lay each leaf on a cutting board and cut off the stem that extends from the bottom of the leave. When the water is at a gentle boil, submerge 2-3 leaves at a time and cook for about 1 minute. Remove from water with tongs and place on a paper towel to dry.

To make the tahini sauce, stir all ingredients together in a small bowl. Add enough water to thin to desired consistency. Should be able to drizzle with a spoon.

To assemble the tacos, lay a leaf flat on a plate, and fill with peppers, onions and mushrooms. Sprinkle hash browns on top and drizzle with Tahini Sauce. Fold up sides of leaf and eat!