Spanish Chickpea Gratin

Name: Spanish Chickpea Gratin
Ingredients: For the gratin:; 2 tablespoons olive oil; 4 medium red onions, halved and thinly sliced; 2-3 cloves garlic, thinly sliced; Salt and freshly ground black pepper, to taste; 2 tablespoons all-purpose flour; 1/4 cup dry sherry; 1 cup vegetable broth; 2 (15-ounce) cans chickpeas, drained and rinsed; 1 pound fresh spinach, roughly chopped; For the breadcrumbs:; 1/4 cup olive oil; 2-3 cloves garlic; 1 tablespoon sweet smoked paprika (pimentón dulce); Salt and freshly ground pepper, to taste; 2 slices rye bread (preferably stale), torn into pieces