Marry Me Chicken Salad Sandwich

Ingredients

• 1 cup mayonnaise

• 2 tablespoons finely chopped shallot

• 1 tablespoon Dijon mustard

• 1 tablespoon tomato paste

• 2 teaspoons garlic powder

• 2 teaspoons white wine vinegar

• 1 1/2 teaspoons kosher salt

• 1 teaspoon dried italian seasoning

• 1/2 teaspoon black pepper

• 1 (7- to 8.5-ounce) jar julienne-cut sundried tomatoes packed in oil (about 1 cup), plus 1 tablespoon oil from jar, divided 

• 2 ounces Parmesan cheese, grated (about 1/2 cup)

• 3 cups (about 1 pound) coarsely shredded or chopped cooked chicken 

• 1/2 cup finely chopped celery

• 2 tablespoons chopped fresh basil

• 8 slices soft whole-grain bread

• 2 cups loosely packed baby arugula or spinach (about 1 1/2 ounces)