Kale Buttermilk Caesar Salad with Chicken

2 tablespoons extra-virgin olive oil 3 ounces whole-wheat bread, torn into 1-inch pieces (about 2 cups) 2/3 cup low-fat buttermilk 1/4 cup grated Parmesan (about 1 ounce) 2 tablespoons reduced-fat sour cream 1 lemon, 1/2 juiced (1 tablespoon juice) and 1/2 cut into 4 wedges 1 small clove garlic, grated Kosher salt and freshly ground black pepper 12 ounces cooked shredded chicken 1 large bunch kale (about 1 pound), stems discarded, leaves thinly sliced