Combine the couscous with 1 cup of boiling water. Bring to a simmer and then cover, turn off the heat. Let it sit for 5 minutes, uncover and fluff with a fork.
Meanwhile, make the pesto: in a blender container, combine the mint, feta cheese, lemon juice, olive oil, salt, and pepper. Blend until smooth.
To cook the broccoli and peas, fill a pot with enough water to cover the broccoli, add the remaining salt and bring to a boil. Add the broccoli, boil for about 3 to 5 minutes just until broccoli is crisp-tender.
Add the frozen peas, stir, then immediately drain the broccoli and peas into a colander.
To assemble in a large bowl, combine couscous, broccoli, peas, walnuts, feta and toss with two forks to combine. This dish can be served warm or cold.