Preheat oven to 400 degrees. In a medium bowl, whisk together honey, 3 tablespoons vinegar, and 2 tablespoons oil; season with salt and pepper. Arrange pears and shallots in a single layer in a small roasting pan; pour honey mixture on top, and toss well to coat. Cook until pears and shallots are easily pierced with the tip of a paring knife, about 30 minutes, turning them over halfway through.

Meanwhile, make vinaigrette: In a small bowl, whisk together remaining 2 tablespoons vinegar, 3 tablespoons oil, and mustard; season with salt and pepper.

Remove roasted pears and shallots from roasting pan. Place pan over high heat; add the water, and cook, scraping up any browned bits from bottom of pan with a wooden spoon, until liquid is reduced by half. Whisk mixture into vinaigrette.

Toss salad greens with vinaigrette. Divide among plates, and arrange pears, shallots, and walnuts alongside.

Toasting walnuts enhances their flavor. Spread nuts evenly on a baking sheet, and toast in a 350-degree oven, stirring occasionally, until fragrant, about 10 minutes. Transfer to a plate to cool.