Preheat oven to 375 degrees F.
Place dry, clean, whole beets on sheet pan lined with parchment paper.
Brush with canola oil; season to taste with sea salt and pepper. Place in oven; roast until cooked, but firm. Remove from oven; cool.
Meanwhile, prepare dressing. Place vinegar in small bowl; whisk in mustard and Maggi Sauce. Slowly drizzle in walnut oil and canola oil, whisking constantly to incorporate. Season to taste with sea salt and pepper. Gently stir in dill seeds and chives.
Peel cooled beets and cut in quarters. Place in large bowl with onions and add a liberal amount of the dressing. Chill for 1 hour or as long as overnight.
Reserve remaining dressing in refrigerator until serving time. Before serving, toss greens with desired amount of dressing and place on individual plates. Top with pickled beets and serve.