For the dressing, combine all ingredients in Mason jar, shake well, and adjust salt and pepper.
Preheat oven to 375˚F. Arrange bacon on slotted pan and bake to extra-crisp, about 18-20 minutes. Chop bacon into 1½ inch pieces, bite-sized. Raise heat to 425˚F.
For the mushrooms, spray the caps on both sides with cooking spray and roast cap-side up on parchment-lined baking sheet 10-12 minutes. Remove, cool, flip and season with salt and pepper. Combine crab with Old Bay, thyme, Dijon, garlic, celery leaves, pimientos, scallions, Tabasco and Worcestershire. Fill caps and mound them up. Mix panko with minced flat parsley and paprika. Top the stuffing with panko mixture, then Gruyere; bake about 18 minutes to deeply golden and cheese is melted.
When you are ready to serve, dress the spinach and kale in large bowl and serve from it or arrange the greens on very large cutting board. Arrange the toppings: bacon, red onion, hard-boiled eggs, almonds and cornichons. Serve with stuffed mushrooms alongside.