- 8 slices bacon (from 3/4 pound)
- 3 1/2 cups (7 sticks) unsalted butter, divided
- 16 cups fresh spinach, stems removed, washed well, and dried (less than 6 pounds total)
- 4 cups watercress, thick stems trimmed, washed well, and dried (about 1 large bunch)
- 8 cloves garlic, peeled and smashed with back of knife
- 2 tablespoons kosher salt
- 2 1/2 teaspoons freshly ground black pepper
- 2 1/2 lemons, thinly sliced into disks
- 30 medium blue point or Malpeque oysters, freshly shucked
- 1 stick licorice root (optional)
- Preheat oven to 350°F. Line large rimmed baking sheet with parchment paper.
- Make three diagonal cuts (at a roughly 45° angle) in each slice bacon, forming 4 diamonds out of each slice (32 diamonds total). Place diamonds on baking sheet and cover with another piece parchment paper. Place another sheet pan on top of parchment. Bake until brown and crispy, about 20 minutes. Transfer to paper towel and pat dry.
- In large skillet over moderate heat, heat 2 tablespoons butter until light golden brown, about 3 to 4 minutes. Add 4 cups spinach, 1 cup watercress, 2 cloves garlic, 1 teaspoon salt, and 1/2 teaspoon pepper. Sauté, stirring occasionally, until greens are just wilted, about 2 to 3 minutes. Remove garlic and discard. Transfer greens to colander set in sink, pressing to extract excess liquid, then transfer to chopping board. Do not wipe out pan. Sauté remaining spinach and watercress in same manner, working in 3 additional batches. Finely chop greens and cover loosely with foil to keep warm.
- Cut remaining butter into 1-inch pieces. In medium saucepan over moderate heat bring 5 tablespoons water to simmer. Reduce heat to moderately low and whisk in butter, one piece at a time, whisking constantly and adding each new piece before previous one has completely melted. Occasionally lift pan from heat to cool mixture and keep it from separating. (Mixture should be consistency of hollandaise.) Remove from heat, add lemon slices, cover, and let steep 15 minutes.
- Remove lemon slices from sauce and stir in remaining 2 teaspoons salt and 1/2 teaspoon pepper. Place over moderate heat and bring to simmer. Add 10 oysters and poach until edges begin to curl slightly, about 30 seconds. Using slotted spoon, transfer oysters to small bowl and cover loosely with foil to keep warm. Poach remaining oysters in same manner, working in 2 additional batches. Do not discard butter poaching liquid. On each of 10 plates, arrange three small piles greens. Place an oyster on each pile, spoon butter sauce over, and garnish with 1 bacon diamond. If desired, finely grate licorice root over top and serve immediately.