How to Make It
Preheat the oven to 375°. On a baking sheet, toss the beans with 1 tablespoon of the oil and season with salt and pepper. Roast for about 30 minutes, stirring, until dry and crispy. Transfer the sheet to a rack and let the beans cool completely.
In a bowl, whisk the mustard, lemon juice and shallot. Whisking constantly, slowly drizzle in 6 tablespoons of the oil; season with salt and pepper. Set the escarole on top; don’t mix.
In a nonstick skillet, heat the remaining 2 tablespoons of oil. Add the shiitakes and cook over moderately high heat, stirring, until golden and charred in spots, 3 to 4 minutes. Stir in the garlic for 1 minute. Add the hot mushrooms, celery, lentils and the chopped chives to the escarole and toss. Mound the salad on plates, top with the crispy beans and serve.