In a large bowl, whisk together vinegar, mustard, maple syrup and a large pinch each of salt and pepper. Drop in garlic cloves, stir, and set aside 15 to 30 minutes to let the flavor infuse.
Step 2
Gradually whisk in oil; dressing will emulsify. Mix in chickpeas, celery and scallions. Cover and refrigerate at least 2 hours or overnight.
Step 3
Remove garlic cloves from dressing. Taste and adjust the seasonings with salt, pepper, vinegar and olive oil. Set aside to come to cool room temperature.
Step 4
If desired, make croutons, for serving: Heat oven to 400 degrees. Pull the soft bread out of the center of the loaf, leaving most of the crust behind, and tear bread into bite-size pieces. You should have about 3 cups. Spread pieces on a rimmed baking sheet and bake for about 12 minutes, until golden and crisp; let cool.
Step 5
Just before serving, mix celery leaves, tomatoes, basil and croutons, if using, into the salad. In a serving bowl, place a layer of greens, if using, in the bottom. Add celery mixture, then top with cheese and more black pepper.