Ditalini with Chickpeas and Garlic-Rosemary Oil

INGREDIENTS

• 1 medium onion, quartered
• 1 medium carrot, peeled, cut into 1-inch pieces
• 1 celery stalk, cut into 1-inch pieces
• 6 garlic cloves, 4 whole, 2 chopped
• 1/2 flat-leaf parsley leaves
• 1/4 crushed red pepper flakes
• 1/2 olive oil, divided
• Kosher salt
• 2 tomato paste
• 2 15-ounce cans chickpeas, rinsed
• 1 ditalini or elbow macaroni
• 1 chopped fresh rosemary