Step 1Rinse the quinoa under cool running water, then drain well with a fine-mesh sieve or cheesecloth-lined strainer (the grains are very small and will slip through a coarse strainer). Heat a wok over medium-high heat and toast the quinoa, shaking the pan frequently, just until the grains dry, are just beginning to color and have a nutty aroma, about 4 minutes. Set aside in a bowl.
Step 2In a medium, lidded pot, bring 1 quart of water to a boil over high heat. Stir in the quinoa with a pinch of salt, then reduce the heat to a simmer and cover. Cook the quinoa until the grains are translucent and tender and the germ has spiraled out from the grain, 12 to 15 minutes (be careful not to overcook). Remove from heat, drain and set aside.
Step 3Meanwhile, heat the wok again over high heat. Add the peanut oil and heat until it just begins to simmer. Stir in the garlic and fry, stirring constantly, just until the garlic is golden, about 30 seconds (the garlic can burn quickly). Remove the garlic with a slotted spoon, keeping the oil in the pan, and set aside.
Step 4Add the fennel to the oil and fry, stirring or tossing frequently, until it is caramelized, 5 to 7 minutes. Remove from the oil and set aside. Add the shiitakes to the oil and stir-fry until caramelized, 4 to 5 minutes. Stir the green onions in with the mushrooms and continue to stir-fry just until the green onions begin to wilt, 1 to 2 minutes. Add the soy sauce and vinegar to the mixture and stir or toss to combine, then remove from heat.
Step 5In a large bowl, gently toss the quinoa with the warm shiitake-green onion mixture, the fennel, garlic, cashews, parsley, cilantro, lime zest and juice. Season to taste with additional salt if desired and serve immediately.