CROUTONS: Preheat the oven to 350 degrees F and adjust the rack to the center position. If using a baguette, cut into 1-inch slices and then tear each slice into 4-6 pieces. Place in a bowl and drizzle with olive oil, melted butter, Italian seasoning, garlic, and salt and pepper to taste (I add 1/4 teaspoon salt and 1/8 teaspoon pepper). Toss to combine and transfer to a lined sheet pan. Bake until crisp and firm but not browned, about 15 minutes. Remove from oven and let fully cool.
DRESSING: Meanwhile, for the dressing, add all the ingredients to a wide-mouth jar. Add salt and pepper to taste. (I add 1/8 teaspoon salt and 1/4 teaspoon pepper but you can always add more salt and pepper to the salad overall.) Shake dressing to combine and then place in the fridge to chill while preparing the rest of the ingredients. Shake the dressing well right before pouring over the salad.
SALAD: In a large bowl, combine the halved cherry tomatoes, halved or quartered mozzarella balls, and the raw corn kernels cut from the cob. (We love it raw and crunchy, but it's also delicious cooked on the grill!) Add the completely cooled croutons and (read instruction #5 before adding dressing) the dressing to taste-- you don't need to use all of it, add to preference. Toss the salad and let stand for about 5-10 minutes, gently tossing, until the bread absorbs the dressing.
SERVE: Right before serving, add the sliced or chopped avocado, basil leaves, and any additional dressing. Season salad to taste with salt and pepper. Add a squeeze of fresh lemon if desired. Serve salad over torn lettuce leaves if desired (not necessary, but does sop up some dressing).
STORAGE: Panzanella doesn’t sit or store well after it’s made. Once assembled, the salad needs to be eaten soon after; otherwise, the dressing will disintegrate the bread, tomatoes will become squishy, and the avocado will brown. To make ahead: Prepare everything (except the avocado), but store ingredients separately in the fridge. Assemble the salad right before eating, adding dressing and avocado right before serving.