Caesar Salad Roast Chicken

Name: Caesar Salad Roast Chicken
Ingredients: 8 anchovies, mashed to a paste; 8 garlic cloves, finely grated; 6 Tbsp. mayonnaise, divided; 1 Tbsp. Dijon mustard, plus more for serving; 2 Tbsp. extra-virgin olive oil, divided; 1½ tsp. freshly ground black pepper, plus more; 1 (3½–4-lb.) whole chicken or 4 chicken legs (thigh and drumstick; about 3 lb.); Kosher salt; 8 medium shallots, unpeeled, halved lengthwise; 2 lemons, divided; 1 oz. Parmesan, finely grated; 4 oz. country-style bread, torn into (1½) pieces; 2 romaine hearts, leaves separated, torn