Preheat oven to 400°F.
Cut ends off of 1 large bulb of garlic to expose the cloves, drizzle the garlic with olive oil and season with salt and pepper. Place garlic in a foil pouch and roast 40-45 minutes until soft and golden. Cool garlic to handle then squish roasted garlic from skins and mash into smooth paste; reserve.
Thinly slice cloves of garlic from another bulb (that’s 7). Finely chop 7 more cloves, the third bulb.
Bring a large pot of water to a boil for spaghetti.
Add 1/3 cup olive oil, 6 turns of the pan in slow stream and 7 cloves of thinly sliced garlic to oil. Turn heat to medium, cook garlic in oil until the sliced garlic turns golden brown and garlic is crispy. Remove garlic chips to plate and reserve garlic oil.
Drop pasta in salted water and cook 7-8 minutes to al dente.
Add 7 cloves of finely chopped garlic to the garlic-infused olive oil over medium heat. Stir in chili pepper and parsley, and season with salt and pepper.
Remove a half-mug of starchy cooking water just before draining pasta, about 3/4 cup.
Add lemon juice to garlic oil and whisk in roasted garlic paste.
Drain spaghetti and toss with garlic sauce while pouring in starchy water, adjust salt and pepper. Top pasta with cheese and crispy garlic chips to serve.