In a medium bowl or measuring cup, combine vinegar and 1/2 teaspoon salt. Stir to dissolve and add onions and tomatoes. Toss to combine, cover, and place in the fridge for a minimum of 30 minutes or overnight.
Make Roasted Garlic Hummus:
Preheat oven to 375 degrees. Place garlic on a small sheet of aluminum foil and drizzle with 2 teaspoons of olive oil. Fold sides of foil to enclose and place on a rimmed baking sheet. Transfer to oven and roast until garlic is caramelized and tender, about 15 minutes.
When cool enough to handle, squeeze cloves from their skins and place in the bowl of a food processor, along with chickpeas, tahini, lemon juice, 3/4 teaspoon salt, and remaining 1/3 cup olive oil. Blend until a thick paste forms. With the mixer running, add ice water and process until until very smooth. Adjust consistency with additional ice water, if desired. Season to taste with salt and additional lemon juice.
Make ancient grain mix:
In a medium saucepan, combine wild rice with 1 cup water and 1/2 teaspoon salt. In another saucepan, combine quinoa with 1 1/3 cups water and 1/2 teaspoon salt. Bring both pots to a boil, reduce to a simmer, and cover. Cook wild rice until tender, about 30-35 minutes. Remove from heat and let steam with lid on for an additional 5 minutes. Remove lid and fluff with a fork. For the quinoa, let cook 15 minutes, until just tender. Do not overcook. Remove lid and continue to cook, stirring occasionally, until any remaining liquid has evaporated. Transfer to a bowl, along with wild rice. Toss to combine.
Make Field of Mushrooms:
Preheat a large cast iron skillet over medium-high heat. Add 3 tablespoons olive oil, swirl to coat pan, and add mushrooms. (If skillet isn’t large enough, this can be done in two half batches.) Increase heat to high and saute, stirring occasionally, until mushrooms begin to turn golden. Season with salt and pepper, add thyme and rosemary, and stir to combine. Make a well in the center of the pan. Drizzle in the remaining 2 teaspoons olive oil and add garlic. Stir to coat and, incorporating mushroom mixture gradually, saute until garlic is softened, about 2 minutes more. Add stock and continue to cook until reduced by half.
Spread a generous dollop of the roasted garlic hummus on the bottom of a serving plate. Top with a portion of ancient grains, pickled onions and tomatoes, and mushrooms. Drizzle with olive oil, top with pepitas, cilantro, and dill, and serve.