artichoke and white bean crostini

4 artichokes, halved lengthwise, tops and stems trimmed, center leaves removed, chokes scraped out
6 cups (or more) low-salt chicken broth
1 cup dry white wine
1/2 cup chopped carrot
1/2 cup chopped onion
1/2 cup chopped celery
2 large fresh thyme sprigs
1 cup drained rinsed canned cannellini (white kidney beans)
1/2 cup grated Pecorino Romano cheese
1/4 cup (packed) finely chopped fresh basil plus whole leaves for garnish
2 tablespoons extra-virgin olive oil plus more for brushing
8 1/3- to 1/2-inch-thick slices pain rustique or other flat country bread
Lemon wedges
Preparation

Bring artichokes, 6 cups broth, and next 5 ingredients to boil in large saucepan, adding more broth if necessary to cover. Reduce heat; cover and simmer until artichoke hearts are very tender, about 50 minutes. Chill artichokes in broth mixture, uncovered, until cold, at least 2 hours and up to 1 day.

Remove artichokes from broth; drain. Pull off leaves. Cut hearts into 1/3-inch cubes; place in large bowl. Mix beans, cheese, 1/4 cup chopped basil, and 2 tablespoons oil into hearts. Season with salt and pepper.

Preheat oven to 400°F. Arrange bread on rimmed baking sheet. Brush with oil. Bake until beginning to crisp, about 8 minutes.

Spoon artichoke topping onto bread. Squeeze lemon juice over; top with basil leaf.