How to Make It
In a medium bowl, cover the nori with the cold water and let stand for 30 minutes. Transfer to a fine sieve to drain, lightly pressing to remove excess water.
Meanwhile, in a mini food processor, combine the garlic, shallot and lemon juice and let stand for 15 minutes. Add the nori, capers, 3 tablespoons of the olive oil and the walnut oil and pulse to a fine paste. Season with salt and pepper. Transfer the “tartare” to a jar and refrigerate for at least 1 hour.
In a steamer basket set over 2 inches of boiling water, steam the potatoes until tender, 12 minutes; transfer to a bowl. Add the haricots verts to the steamer and steam until crisp-tender, 5 minutes. Add the beans to the potatoes, then fold in the nori “tartare” and the remaining 2 tablespoons of olive oil. Season the salad with salt and pepper. Gently fold in the avocado and serve warm.