Preparation Toss cauliflower with 2 tablespoons oil in a shallow baking pan and season with salt. Roast in middle of oven, stirring occasionally, until cauliflower is tender and begins to brown, about 15 minutes. Meanwhile, cook nuts in remaining 2 tablespoons oil in a small skillet over moderately low heat, stirring occasionally, until fragrant and a shade darker, about 5 minutes. Cool slightly in skillet. Stir together lemon juice and mustard in a large bowl. Add nuts with any oil from skillet, roasted cauliflower, watercress, radicchio, and salt and pepper to taste, then toss to coat.
Preparation Toss cauliflower with 2 tablespoons oil in a shallow baking pan and season with salt. Roast in middle of oven, stirring occasionally, until cauliflower is tender and begins to brown, about 15 minutes. Meanwhile, cook nuts in remaining 2 tablespoons oil in a small skillet over moderately low heat, stirring occasionally, until fragrant and a shade darker, about 5 minutes. Cool slightly in skillet. Stir together lemon juice and mustard in a large bowl. Add nuts with any oil from skillet, roasted cauliflower, watercress, radicchio, and salt and pepper to taste, then toss to coat.