Bring a small saucepan of salted water to a boil. Add the shallots and blanch until tender, about 30 seconds. Drain and run the shallots under cold water until cool. Place shallots in a small heat-proof bowl and set aside.

Combine vinegar, salt, and sugar in the same saucepan and bring to a boil, stirring until sugar is dissolved. Pour boiling liquid over shallots and let sit at room temperature until cool. Drain shallots into a strainer set over a medium bowl; set shallots aside.  Add mustard and a little black pepper to the pickling liquid and stir to combine. While whisking, slowly add olive oil until dressing is emulsified.

Cut orange into segments by slicing off the top and bottom of the orange. Then with the orange laying flat on the cutting board, remove the peel by following the curve of the orange with a pairing knife, cutting downward to remove all the peel and white pith. Then slice between the membranes to release the orange segments. Squeeze the juice from the membranes over the bowl of dressing and stir to combine. Slice each segment in half, or thirds if really large.

Combine greens, pomegranates, orange segments and pickled shallots in a large salad bowl. Drizzle about 1/3 of the dressing over the top and toss to combine. Add more dressing and salt and pepper as needed.