Clams with White Beans, Fennel and Broccoli Rabe

INGREDIENTS

• 1 fennel bulb, a few fronds reserved and minced for garnish
• 1/2 tsp. fennel seeds
• 1 Tbs. olive oil, plus more for drizzling
• 1/2 large red onion, finely chopped
• 1/4 to 1/2 tsp. red pepper flakes
• 1/2 cup dry white wine
• 1 can (14 1/2 oz.) cannellini beans, drained, juices reserved
• 1 bottle (8 fl. oz.) clam juice
• Large pinch of saffron threads
• Freshly ground black pepper, to taste
• 1/2 small bunch broccoli rabe or Chinese broccoli, chopped
• 2 lb. Manila clams, rinsed
• Coarse kosher salt, to taste (optional)