Rinse 1 cup quinoa under cold water and drain; combine quinoa, 1 3/4 cups water, and 1/4 teaspoon salt in a medium saucepan and bring to a gentle boil over medium-high heat.

Reduce heat to low, cover, and simmer for 12 minutes without lifting the lid; remove from heat and let sit covered for 10 minutes, then uncover and fluff with a fork.

Bring a medium pot of salted water to a boil, add broccoli florets and blanch for 60–90 seconds until bright green and crisp-tender, then transfer immediately to an ice bath and drain thoroughly; core and dice apples and toss with 1 teaspoon lemon juice.

Whisk olive oil, Dijon, whole-grain mustard, honey, apple cider vinegar, 1/4 teaspoon salt, and 1/4 teaspoon black pepper in a small bowl and warm gently in a skillet over low heat for 30–45 seconds until slightly warm.

Pour the warm dressing over the slightly warm quinoa and fold to coat, then spread on a rimmed baking sheet or let cool in the bowl to room temperature.

Once the quinoa is cool, fold in blanched broccoli, apples, toasted almonds, toasted pecans, and chopped parsley; adjust seasoning and refrigerate for 20 minutes if serving chilled.

Taste and add a splash more vinegar or a pinch of salt if needed; sprinkle optional crumbled feta just before serving if using.