This soup comes together quickly, so its helpful to start with everything prepped. Dice the onion and garlic super small, you're not blending this soup so cut it as small as you're happy to eat it. Finely Chop the Broccoli and Shred the Cheese.
Make the Soup
In a large soup pot/Dutch oven on medium heat add the butter with the onion and garlic. Cook for a few minutes until the onion is tender.
Sprinkle the flour over the onion mix and stir to mix it all in.
Now you will slowly add in the milk and soup stock. The key here is to add just a bit of liquid at a time. Stir to make sure all the flour and liquid are blended and then add it a bit more liquid - repeat until all the liquid is in.
Add in the seasonings, cheese and broccoli. Stir to combine.
Simmer the soup until the broccoli is tender and the soup has thickened up a bit. About 7 minutes.