Heat olive oil in a pot over medium heat.

Add onion and cook until softened, about 3-5 minutes.

Add garlic and celery and cook for another 2 minutes.

Stir in kohlrabi and bay leaf, cook for 4 minutes.

Slowly add water and milk, stirring to combine.

Mix in chicken bouillon granules.

Bring soup to a boil over medium heat, stirring frequently to prevent milk from frothing.

Reduce heat, partially cover, and simmer until kohlrabi is very soft, about 30 minutes.

Remove soup from heat and discard bay leaf.

Fill blender halfway with soup. Cover and hold lid down with a potholder and pulse a few times before blending.

Pour blended soup into a separate pot.

Repeat the blending process with the remaining soup.

Season with salt and pepper to taste.

Return soup to the stove and heat until hot.