Boil the broccoli in the broth, covered, until cooked.
Let cool slightly; enough to safely pour into blender.
Blend until a smooth purée.
In the now-empty pot, add the butter and cook on medium the onions until limp (not browned!).
Add the ground chia seeds and stir until a thin paste starts to form.
Turn element to low, and pour the cream onto the paste.
Stir constantly until cream begins to boil gently and starts to thicken.
Return the broccoli puree to the pot and stir until the whole soup begins to bubble.
Remove from heat and add the cheese;l stir until blended.