Place all of the dressing ingredients into a small mixing bowl and whisk to combine.
For the salad:
Cook the quinoa in the vegetable or chicken stock. Allow to stand for 5 minutes.
Drain any excess liquid and transfer the quinoa to a mixing bowl.
Heat the olive oil in a pan and fry the mushrooms for 3-4 minutes, or until golden brown and tender. Season with salt and pepper. Transfer the mushrooms to the quinoa, with the peas, beetroot, mint and feta cheese, if using.
Pour half of the dressing over the salad and toss to combine.
Arrange the salad onto a serving platter and garnish with pea shoots and mint leaves. Serve with the remaining dressing.