Warm Steak and Potato Salad

INGREDIENTS

• 1 pound new potatoes
• 1 pound beef sirloin steak
• 1/2 teaspoon salt
• 1/4 teaspoon ground black pepper
• 8 cups mixed baby salad greens
• 1 pint cherry tomatoes, halved
• 2 tablespoons minced shallot
• 2 tablespoons olive oil
• 1 tablespoon red wine vinegar
• 1 teaspoon Dijon mustard
• 1/4 teaspoon dried tarragon