Place the quinoa and vegetable stock or water (if using water, season it with 1/2 teaspoon of salt) and bring to the boil over medium high. Reduce heat to medium low, cover and cook until the quinoa is translucent and the liquid has been absorbed, 15 to 17 minutes. Turn off heat and leave for 2 minutes. Transfer to a plate until cooled.
Meanwhile, in a large bowl (large enough for the whole salad) make the dressing. Add the garlic, mustard, cumin seeds, maple syrup, olive oil, vinegar and 2 tablespoons of water and whisk to combine. Season with 1/2 teaspoon of salt and lots of black pepper and whisk again. Check seasonings to make sure it has the right balance of acidity, sweetness and saltiness, adjusting the vinegar, maple and salt if needed.
Chop the fennel fronds. Use as much or as little as you like.
To the bowl with the dressing, add the cooled quinoa, fennel, red onion, cherries, fennel fronds, pistachios, mint and spinach. Toss well to combine. Season with well with sea salt and black pepper. Serve immediately or allow the salad to rest for 20 to 30 minutes before eating (this allows the flavours to meld and the onion and fennel to soften ever so slightly).