Wash the greens: Fill a sink or large basin with tepid water. Remove any wilted or damaged leaves from the butter lettuce, romaine and endive. Trim each head at the root to release whole leaves. Leave butter-lettuce leaves whole, but halve large leaves of romaine and endive on the bias, then drop into water. Trim and discard any roots and long stems off watercress, and drop remaining leaves and tender stems into water. Trim and discard dark green outer leaves and tops from frisée until only light green and white parts remain. Trim at the root to release leaves, and drop into water. Swirl greens in water, then drain. Wash twice more in cool, then cold, water, then transfer to a salad spinner to dry. Gently wrap in clean dish towels, and set aside.

Place the shallot in a fine-mesh strainer, and quickly rinse with cold water. Allow to drain, then place in a medium bowl, and add vinegar and warm water. Allow to sit for 2 minutes, then whisk in oil, mustards, honey (if using), thyme, garlic and a large pinch of salt. Taste, and adjust salt and vinegar as needed.

To serve, gently pile a generous handful of greens into a serving bowl, then sprinkle with salt, pepper and a generous drizzle of dressing. Continue with another handful of salad and more seasoning and dressing, repeating until you have a glorious, gravity-defying mound of salad. Top with a final drizzle of dressing, and serve immediately.

Wrap remaining greens in an airtight container or plastic bag and refrigerate for up to 3 days. Cover and refrigerate remaining dressing for up to 3 days.