Alexis's Egg Salad Sandwich

INGREDIENTS

• 9 hard-boiled eggs, peeled, and roughly chopped
• 1/3 cup homemade or best-quality mayonnaise, plus more for spreading
• 1 medium stalk celery, cut into 1/4-inch dice
• 3/4 teaspoon dry mustard powder, or 1 teaspoon Dijon mustard
• 1/4 teaspoon mild Madras curry powder, (optional)
• Coarse salt and freshly ground black pepper
• 1 small head radicchio or 1 small bunch arugula, washed well and spun dry
• 8 to 12 slices whole-grain bread