If using fresh corn, carefully cut the kernels from the cobs. Chop the onion and mince the garlic.

In a large pot or Dutch oven, melt the butter over medium heat. Add the chopped onion and cook until softened and translucent, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Stir in the corn kernels, salt, black pepper, and optional sugar. Cook for 2-3 minutes, stirring occasionally. Pour in the vegetable broth, bring to a simmer, then reduce heat to low, cover, and cook for 10-12 minutes until the corn is tender.

Carefully transfer about half to two-thirds of the soup mixture to an upright blender, or use an immersion blender directly in the pot. Blend until mostly smooth, leaving some texture if desired. For a completely smooth soup, blend all of it. Be cautious when blending hot liquids; vent the blender lid and cover with a towel.

Return the blended soup to the pot (if using an upright blender). Stir in the milk and heavy cream (if using). Heat gently over low heat until warmed through, but do not boil. Taste and adjust seasoning as needed.

Ladle the hot corn soup into bowls. Garnish with fresh chives, crumbled bacon, and a pinch of red pepper flakes, if desired. Serve immediately.