Heat the olive oil in a large pot or Dutch oven over medium heat. Add the chopped yellow onion and cook, stirring occasionally, 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.

Add the cauliflower florets to the pot. Pour in the vegetable broth, ensuring the cauliflower is mostly submerged. If not, add a little more broth or water.

Bring the mixture to a boil, then reduce the heat to low, cover, and simmer for 15-20 minutes, or until the cauliflower is very tender when pierced with a fork.

Carefully transfer the soup mixture to a blender. You may need to do this in batches depending on the size of your blender. Alternatively, use an immersion blender directly in the pot. Blend until the soup is completely smooth and creamy. For an extra-velvety texture, you can strain the soup through a fine-mesh sieve after blending, although this is optional.

Return the blended soup to the pot (if you used a countertop blender). Stir in the milk and heat gently over low heat, without boiling. Season with salt and black pepper to taste. If the soup is too thick, you can add a little more milk or broth to reach your desired consistency.

Ladle the hot soup into bowls. Garnish with your favorite toppings such as fresh chives, chopped parsley, a drizzle of cream or olive oil, or toasted croutons. Enjoy your delicious Creamy Cauliflower Soup!