To roast the garlic, cut tops off the garlic heads. Put garlic into a small ovenproof dish, sprinkle with a little salt and pepper, and spray the top of the garlic with olive oil spray. Pour 3 table­spoons of chicken stock over the garlic and cover dish tightly with foil. Put into a 300° oven for 1 1/2 hours. When garlic is done, remove, let cool slightly, squeeze garlic out, and mash. Reserve.
Saut├® leeks in butter for 2 minutes. Add 2 tablespoons flour that has been mixed with ┬╝ cup hot water and blend. Whisk in 4 cups of chicken stock and milk. Add mashed potatoes, diced potatoes, roasted garlic puree, and cilantro. Cook 40 minutes.
Reduce heat to simmer and blend in evaporated milk. Sea­son with salt and pepper to taste.