Wash and dry the Brussels sprouts. Slice thinly with a sharp knife oruse a mandoline.
Add the Brussels sprouts and spinach leaves to a bowl.
Toast the pumpkin seed kernels in a dry sauté pan over medium heatuntil they become fragrant and slightly darker (about 3 minutes). Add themto the bowl with the greens. Toss the ingredients to fully combine. Add feta and tossgently just until combined.
Top the salad with pomegranate arils, a sprinkling of feta, and a drizzle of vinaigrette.
Add the pomegranate juice, sugar, and lemon juice to a small sauce pan over medium-low heat. Cook, stirring occasionally, until liquid reduces to ¼ cup (about 20-25minutes). Cool slightly.
Add the liquid, apple cider vinegar, and mustard to a small bowl. Briskly whisk themixture while slowly drizzling in the olive oil.