pasta and white beans with garlic-rosemary oil

INGREDIENTS

• 1 medium onion, cut into big chunks
• 1 medium carrot, in big chunks
• 1 celery stalk, in big chunks
• 6 garlic cloves, 4 left whole, 2 finely chopped
• 1/2 cup flat-leaf parsley leaves
• 1/4 teaspoon crushed red pepper flakes (or to taste)
• 1/2 cup olive oil, divided
• Coarse or kosh salt
• 2 to 3 tablespoons tomato paste
• 3 1/2 cups cooked, drained beans (save cooking liquid for water in recipe, if desired) or 2 15-ounce cans small white beans (such as Great Northern or Cannelini), rinsed
• 1 pound short tube pasta (see suggestions above)
• 1 tablespoon minced fresh rosemary