Combine onions, garlic, chicken broth, and potatoes in a large stock pot. Boil until potatoes can be partially mashed with the back of a spoon, about 10 minutes.
Gently steam frozen broccoli in the microwave so it is soft enough to chop. Add to boiling vegetables for 5 minutes of cooking.
Reduce heat to a simmer and add milk and cream cheese, slowly stirring until the cream cheese is melted.