How to Make It
Preheat the oven to 400°. In a large skillet, bring the clam juice to a boil with the bay leaves. Add the mussels, cover and cook over high heat until they open, about 2 minutes; discard any that remain closed. Shell the mussels and place in a bowl. Strain the cooking liquid over them and let cool.
In a small bowl, combine the olive oil and butter and brush on both sides of the bread. Toast the bread on a baking sheet in the oven for about 10 minutes, or until golden brown and crisp. Rub the warm toast on both sides with the cut garlic clove. Cut the toast into 1-inch dice.
In a small bowl, whisk the mayonnaise with 2 tablespoons of the mussel cooking liquid. Add the lemon juice, Aleppo pepper and a pinch of salt.
Lift the mussels from the liquid with a slotted spoon and transfer them to a medium bowl. Add the tomatoes, parsley, chives and tarragon and toss. Add the croutons, mâche, spinach, watercress and the dressing and toss again. Mound the salad on 4 plates and serve.