Rinse the Brussels sprouts, and dry them on a towel.
Cut off the stems of the sprouts, then cut them in half, top to bottom.
Lay the sprouts on their flat sides, and thinly slice them. Then, place them into a large bowl.
Mix the red wine vinegar, agave nectar, whole grain mustard, olive oil, salt, and freshly ground black pepper in a lidded jar or bowl. Shake or whisk the dressing ingredients until emulsified.
Pour the dressing over the Brussels sprouts, and toss.
Chop the dates and Manchego.
Reserve a small amount of the dates, cheese, and sunflower seeds for garnishing the salad.
Mix the rest of the dates, cheese, and seeds with the Brussels sprouts, and toss the salad.
Top the salad with the reserved dates, cheese, and seeds.