Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees.

Drain and rinse chickpeas; pat very dry with paper towels. Halve, peel, and cut shallot into ½-inch-thick wedges.

Toss chickpeas and shallot on a baking sheet with a drizzle of oil, half the Italian Seasoning (all for 4), salt, and pepper.

Roast on top rack until chickpeas are golden and tender and shallot is caramelized, 18-20 minutes. (You’ll add more to the sheet after 11 minutes.)

Meanwhile, wash and dry produce.

Halve tomatoes. Dice mozzarella into ½-inch cubes.

Place tomatoes in a small bowl; toss with vinegar, 1 tsp sugar (2 tsp for 4 servings), and a big pinch of salt.

Halve ciabatta lengthwise; cut into ¾-inch strips. Tear strips into rough cubes. Transfer to a large bowl; toss with 2 TBSP olive oil (4 TBSP for 4 servings), garlic powder, salt, and pepper.

Once chickpeas and shallot have roasted 11 minutes, remove from oven and push to one side of sheet; carefully add croutons to empty side. (For 4, add croutons to a second sheet; toast on middle rack.) Return to top rack until golden and crispy, 7-9 minutes. Wipe out bowl.

Carefully transfer everything to bowl used to season croutons to cool.

Remove tomatoes from bowl and set aside, leaving marinade behind.

Whisk half the mayonnaise and half the mustard into marinade until smooth. (For 4 servings, use all the mayonnaise and mustard.)

Slowly whisk in 4 TBSP olive oil (8 TBSP for 4), drizzling a little bit at a time, until creamy. Season with salt and pepper. Reserve 1½ TBSP dressing (3 TBSP for 4) for serving.

Add spinach to bowl with cooled chickpeas, shallot, and croutons. Toss with remaining dressing until evenly coated.

Divide salad between plates. Top with mozzarella and tomatoes. Drizzle with reserved dressing and season with salt and pepper. Serve.