Place water and 1 tablespoon salt in a large pot. Submerge husked ears of corn and let soak for 20 to 30 minutes. Remove corn from water and preheat grill.
Place corn on grill and cook, about 5 to 6 minutes per side, until kernels are charred and toasty. Remove from grill and cool.
With a sharp knife, remove grilled corn kernels from cobs. Set aside. Place cleaned corn cobs back into the pot with the water and salt. Bring to a boil, cover, and simmer 20 minutes. Remove cobs and discard.
Melt butter in a sautée pan. Cook onion and garlic over medium-low heat until translucent, about 4 minutes.
Set aside 1 cup of corn kernels. Add the remaining grilled corn to the pot of corn stock. Add the sautéed onion and garlic, and milk to the pot. Bring to a light boil and simmer 15 minutes.
With a hand blender or a stand-up blender, carefully purée the hot soup until smooth.
Sieve the soup through a medium-mesh strainer. Press firmly on any remaining corn solids to extract all pulp from soup. Discard pulp. Add remaining salt and pepper to taste.
Add reserved 1 cup of corn kernels, plus cooked crumbled bacon, and serve
Finishing your grilled corn soup with a drizzle of white truffle oil adds another layer of flavour depth and richness.