Basil Chicken Salad with Mushrooms, Walnuts, and Avocado on a Whole Grain Bread

Ingredients

• 3 chicken breast halves, about 1 1/2 lb. total, cooked (roasted)
• 1/4 cup of fresh basil leaves, chopped
• 2 scallions chopped
• 1 small red onion, diced (more for serving, optional)
• 1 large avocado, firm but ripe, pitted, peeled and diced (more for serving, optional)
• 3/4 lb. mushrooms of your choice
• 2 Tbsp. butter
• 1/2 cup walnuts, toasted and chopped
• 1/4 cup mayonnaise 
• juice of 1/2 lemon
• salt and freshly ground black pepper
• 4 slices of Whole Grain Bread, toasted