How to Make It
Squeeze the lemon juice into a bowl of cold water; add the lemon to the bowl. Using a sharp stainless-steel knife, cut off the artichoke stems and halve the artichokes crosswise. Discard the tops. Working with 1 artichoke at a time, pull off all the outer green leaves from the bottoms until you reach the yellow leaves. Trim off the tough outer skin. Scrape out the hairy choke with a teaspoon, then drop the artichoke hearts into the lemon water.
Heat 1/2 tablespoon of the olive oil in a medium saucepan. Add the bacon and cook over low heat, stirring until the fat begins to melt, about 4 minutes. Stir in the garlic, carrot and onion. Cover and cook over low heat until the vegetables are softened, about 8 minutes. Add the remaining 1 1/2 tablespoons of olive oil and the artichoke hearts. Stir in the Riesling, water, thyme and bay leaf and bring to a boil. Season with salt and pepper and simmer over low heat until the artichoke hearts are tender, about 15 minutes.
Using a slotted spoon, transfer the artichoke hearts to a plate. Skim 1 1/2 tablespoons of oil from the artichoke broth and put the oil in a small bowl. Crumble the saffron threads into the oil. Strain the artichoke broth. Pour 1/2 cup of the broth into the saucepan and boil over high heat until reduced by half, about 3 minutes. Discard any remaining artichoke broth.
Cut 1 artichoke heart in half and cut 1 of the halves into chunks. Transfer the artichoke chunks to a blender. Add the reduced broth and puree. With the machine on, slowly add the saffron oil and blend until smooth. Scrape the puree into a small bowl and stir in the sherry vinegar and lemon juice. Season with salt and pepper.
Thinly slice the remaining 2 1/2 artichoke hearts. In a medium bowl, toss the lettuce with 1 tablespoon of the vinaigrette and arrange it on 2 plates. Top the Bibb lettuce with the sliced artichokes and drizzle with the remaining saffron vinaigrette and serve.