Heirloom Tomato and Cornbread Panzanella

Name: Heirloom Tomato and Cornbread Panzanella
Ingredients: 3 (heaping) cups 1-inch cubes of day-old cornbread (see headnote) — don’t be shy with these, this isn’t called bread salad for nothing; Olive oil; Kosher salt and freshly ground pepper; 2 pounds heirloom tomatoes in a variety of colors (get the weirdest and most bulbous S.O.B.s you can find at the farmers market—that’s how you win summer), chopped into 1- to 2-inch pieces; 1 shallot, peeled and minced; 3 tablespoons balsamic vinegar; 4 to 5 ounces fresh mozzarella, torn into bite-sized pieces; 1/2 cup (packed) basil, torn; Flaky sea salt, to finish