Preheat oven to 400˚F.
Slice off the top of the head of garlic.
Place the leeks, cauliflower, broccoli, zucchini, potatoes and garlic on a large sheet pan. Drizzle with olive oil, 1 tsp salt and pepper. Roast for 30 minutes, until all vegetables are fork tender.
About 10 minutes before the vegetables are done, add the broth and peas to a small pot and heat until simmering.
Use the crouton ingredients to make a grilled cheese sandwich. Cut the sandwich into cubes.
Add everything (only add half of the garlic cloves) to a blender, including remaining ½-1 tsp salt (depends on your preference and type of salt used) and blend until smooth.