Preheat oven to 400˚F.

Slice off the top of the head of garlic, exposing the cloves.

Place the leeks, cauliflower, broccoli, zucchini, potatoes and garlic on a large sheet pan. Drizzle with olive oil, 1 tsp salt and pepper and toss gently. 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.

Add all of the vegetables (only add half of the garlic cloves) to a blender, along with the hot broth + peas, lemon juice, spinach, parsley, remaining ½-1 tsp salt (this depends on your preference and type of salt used) and red pepper flakes and blend until smooth.

To make grilled cheese croutons, add butter to a pan over medium low heat. Begin toasting bread in the pan until it's golden brown and caramelized, then flip one piece over and add 2 cheese slices to the caramelized surface. Spread the pesto on top of the cheese, then place the other 2 cheese slices on top (this prevents the bread from getting soggy). Place the other slice, cooked side down, on top of the cheese.

Cover with a lid. Cook until bottom is brown and crispy, then flip again and cook until other side is brown and crispy, and cheese is completely melted. Remove from heat and slice into small cubes.