Preparation

• Position a rack in the center of the oven and heat the oven to 450°F.
• Combine 1 Tbs. of the oil, the cayenne, and 1/4 tsp. salt in a small bowl. Put the bread cubes on a rimmed baking sheet and toss to coat with the cayenne oil. Toast in a single layer until lightly crunchy and golden brown, 6 to 8 minutes. Set aside.
• Meanwhile, in a dry 8-inch skillet over medium heat, cook the prosciutto, stirring occasionally, until crisp, about 4 minutes. Set aside.
• In a small bowl, whisk the vinegar, curry powder, syrup, mustard, and 3/4 tsp. salt. Slowly whisk in the remaining 3 Tbs. oil. Season to taste with more salt.
• In a large bowl, toss the croutons with 1/4 cup of the vinaigrette to soften them slightly. Add the watercress and toss again. Divide among four plates. Put the eggs and onion in the bowl, toss with the remaining vinaigrette, and season to taste with salt. Top the salads with the egg mixture. Sprinkle with the prosciutto and tarragon and serve.