3/4 cup extra-virgin olive oil
1/2 cup (packed) pitted Kalamata olives
5 tablespoons red wine vinegar
5 ounces mizuna, ends trimmed, or mixed greens
3 pounds heirloom tomatoes (preferably assorted colors and shapes), cut into slices and wedges
1 pound burrata cheese* (4 small balls) or fresh water-packed mozzarella
1/4 cup thinly sliced fresh basil plus whole leaves for garnish
*Burrata (fresh mozzarella filled with cream and curds) can be found at some supermarkets and at specialty foods stores, Italian markets, and cheese shops.