Marinate the lamb loin in the marjoram, thyme, lemon zest and olive oil for at least 1 hour and up to 24 hours.
Preheat the grill and season lamb with sea salt and freshly ground pepper. Grill to 136˚ for medium, approximately six to seven minutes per side. Keep grilled lamb loin loosely tented with foil in a warm area of the kitchen.
Place sliced ginger in a non-reactive bowl. In a small sauce pot, bring honey, star anise, rice wine vinegar and sea salt to a boil. Pour over ginger and refrigerate for minimum of 30 minutes. The pickled ginger will keep up to one week, refrigerated.
In a non-reactive skillet over medium heat, sweat black garlic and shallots in walnut oil and butter until shallots are translucent, add mushrooms and cook while stirring until moisture has nearly evaporated. Add Madeira and sherry vinegar then cook down again until nearly dry. Fold in tarragon and honey. Season with salt and pepper and set aside.
Prepare an ice bath. Bring a pot of salted water to a rapid boil. Blanch the peas until just cooked through, approximately two minutes after the water recovers to a boil. When tender, shock peas in the ice bath, drain and reserve in a non-reactive bowl. Add the pea tendrils and blossoms.
To plate, divide mushroom duxelle equally between dishes. Arrange the thinly sliced lamb over both, top with pickled ginger and garnish with spring peas, fleur de sel and spring fruit tree blossoms.