1. If using bacon, cook it in a skillet for several minutes, until crisp. Remove bacon from pan and set aside to drain on paper towels.
2. Add the onion to the skillet with the bacon fat and cook over low-medium heat until well caramelized, 10-15 minutes (if leaving the bacon out of the salad, cook your red onion in a couple of tablespoons of olive oil instead). Toss the pea sprouts/shoots into the pan with the onion for the last minute or two of cooking. Take off the heat and allow to cool.
3. Crumble or chop the bacon and mix it with the spinach, onions, and pea shoots in a medium-large bowl. Compose salad on plate(s), then garnish with the blue cheese, the walnuts, and the violets. Drizzle the salad with walnut or olive oil, and add a little balsamic vinegar or fresh lemon if you like, as well.