Quinoa's a funky little grain. It looks like a bunch of tiny round balls. With tails. Little curly-cue tails. It tastes a little bit nutty, a little bit grainy. Originally from South America, this weird little grain is an ancient source of high-quality, unusually complete protein (at 12-18%, with a high concentration of amino acids compared to wheat or rice). It's also a good source of dietary fiber, phosphorous, magnesium and iron - and is gluten-free. But the best part about eating quinoa is that it goes really well with feta cheese. Mmmmm...cheeeeeese....
Rinse the quinoa well in whatever manner you choose.
Bring the water to a boil and pour the quinoa in. Reduce heat to just-above-simmer and cook until all water has been absorbed and the quinoa is done - about 15-20 minutes. You can also cook quinoa in a rice cooker.
Let the quinoa cool and then toss with all the salad ingredients except the cheese.
To make the dressing: in a small bowl, whisk the mustard and vinegar together until smooth. Drizzle the olive oil in, whisking constantly, until the mixture is emulsified. Add salt and pepper to taste.
Alternately, dump all the dressing ingredients into one of those Hidden Valley cruet thingies or into a container with a lid that you trust will stay tight on, and shake the hell out of it 'til it's all blended nicely.
Pour dressing over salad, toss to mix, adjust seasonings. Fold cheese in carefully at the end. Or dump in a bunch unceremoniously. You know - by "accident."